Out of this world: Herman and Erica Cornejo are poised for stardom at ABT.

The streak of white soaring above the stage knows no gravity. When Herman Cornejo begins his solo as the newly married Franz in American Ballet Theatre's Coppelia, the familiar music and pastel sets melt away. His effortless triple turns and jumps seem an ebullient outpouring of young love triumphant. It's a remarkable moment, all the more striking for Coppelia's artifice. Just minutes before, his sister Erica has finished leading a czardas with a zest that might make any Mittel European homesick. When the Cornejos dance, it's never merely a variation--it's a complete performance.

ABT's recent New York season brought the Cornejos , and particularly Herman, fervent applause and almost as fervent reviews. Yet neither conforms to prevailing ballet aesthetics. While Herman, 23 and a principal, has extraordinary technique, his purity and classicism set him apart from many virtuosos. Erica, 25 and a soloist, flows through phrasing so musically it seems as though the steps come to her like breathing, but she lacks the hyperextension favored in ballerinas today. The Cornejos are succeeding despite ballet's current emphasis on brash athleticism, winning gradual opportunities rather than overnight stardom.

Brother and sister are small and compact, but different in their qualities. "Herman has natural elegance and an incredible refinement to his technical brilliance," says ABT ballet master Kirk Peterson, who has coached both dancers. "He is at home in the air, which is what people always said of Nijinsky. Erica is a perfect contender for the Romantic school. She's a very open performer and she, too, has an easy jump. She's wonderful at that quick footwork you see in ballets like Giselle. That's not part of most ballerinas' bag of tricks anymore."

The Cornejos credit their abilities to their training at the Superior Institute of Art at the Colon Theater in Buenos Aires. Erica began dancing when she was 4, asking her mother if she could go to the ballet school across the street from her kindergarten. A few years later, her brother came to school one day, heard the music, and started dancing. He immediately wanted to begin class, and his parents, though surprised at a shy child's sudden transformation, were willing. Eventually both children were admitted to the Colon Theater's school.

There they studied ballet, folk dance, French, the history of ballet, and later on, partnering. Since they lived in a distant suburb, they got up at 4 AM to make it to the city in time for a 7:30-AM class. They often didn't return home until 11 PM, putting in a half-day of regular school between ballet lessons. Many times they slept only four or five hours a night.

Despite the grueling schedule, neither considered quitting. "When they talk about our dancing, they say sometimes, 'You have Latin blood,'" Herman says. "But I think it's because we really wanted to do it. We left everything behind to dance--friends, family, soccer, which I loved. I think that's what we project onstage. It comes from here," he adds, as he gently touches his heart.

Erica traces their sense of commitment to her childhood memories of her father, an amateur high jumper, studying deep into the night for his army entrance exams. Both children worked hard to be at the top of all their classes at Teatro Colon--"The French exams were really tough because the teacher insisted everything be exactly right," Herman remembers. Their mother shepherded them from school to school, while their father, now a major in the Argentine air force, worked his way up through the ranks, taking a job as a security guard at night to pay for his childrens' dance lessons, clothing, and Erica's pointe shoes. Herman began entering South American dance competitions when he was 10, and Erica joined Julio Bocca's touring company when she was 14. Herman entered the company soon afterward. "We knew we would get a lot of time onstage, and we'd be paid and that would help with the bills, " Erica explains.

Trying out for ABT seemed a logical next step after several years with Bocca, and both dancers were admitted to the Studio Company after they auditioned in 1998. Within a few months, they moved to the corps de ballet. The siblings' perfectionism struck their colleagues as much as their technique. "They take ballet really seriously," says ABT principal Ethan Stiefel. "I've been in performances with Herman where he wasn't satisfied with what he did--it might be something another dancer wouldn't give a second thought about--and he'll clearly be upset."

Steadily seeking to improve, Erica and Herman give each other detailed corrections. "I've seen from the audience the little things that are missing in a performance," Erica says. "So I always ask Herman, 'Please tell me if you see something could be better.'" Herman echoes her: "A coach will see it all, but may not say it. The audience may clap, but I know." The siblings also turn frequently to their offstage partners for corrections--Herman is dating ABT soloist Carmen Corella, while Erica is engaged to Boston Ballet principal Carlos Molina.

Despite their intense focus, brother and sister are soft-spoken and courteous. "Herman is like Clark Kent stepping into a phone booth," jokes ABT artistic director Kevin McKenzie. "Onstage he has this expansive confidence as he flies around; offstage he's polite and self-effacing." While MeKenzie notes the joy Erica projects onstage, her coaches say that in the studio she can be thoughtful. She faces more hurdles than Herman, despite reviews this past season like one from The New York Times' Anna Kisselgoff that praised her "superb" dancing in Raymonda's Saracen duet. "Generally, she's not thought of as a tutu dancer," says Peterson. "She's working on elongating her line, but she needs to be given roles that will help her develop." Erica takes Pilates to help make her line more attractive, but she remains clear-eyed about her goal. "You have to get better and better for yourself, not to impress someone else," she says.

The Cornejos deeply admire Vladimir Vasiliev and Ekaterina Maximova, the celebrated Bolshoi couple who perforated classics like Giselle and Romeo and ballet around the world, including the Teatro Colon, where Herman once was cast in Anyuta as Vasiliev's son. "They were stars beyond technique," Erica remembers. "They were expressive--a light came from their bodies."

A few critics are beginning to have a similar reaction to Herman. Kisselgoff wrote that his performance in Coppelia "moved onto a spiritual plane," which should gratify a dancer who sees physical accomplishments as a means to an end. Robert Gottlieb praised his virtuosity and charm as Mercutio. "Jumping or turning doesn't make you an artist," Herman says. "Interpreting does." Brother and sister yearn for dramatic roles like the ones in which their idols triumphed--Herman to perform a classical lead like Solar in La Bayadere, Erica to dance Juliet or Tatiana in Onegin. "When I see those ballets, I want to explode," she says. "I want to express those feelings, to make the audience cry."

In a company crammed with talent--and ever-taller ballerinas that poses a challenge. "I don't think finding the right partner is the next step for Herman," says McKenzie. "While it's not out of the realm of possibility that he would dance the classics, the mission for me is to create a role specific to him that would add to the canon of ballet." With Herman and several other dancers in mind, he notes, ABT will restage Petrushka next year.

With their thrilling blend of classicism and ardor, the Cornejos are a throwback to another era, when ballet had a magic that transcended bravura spins and quadruple pirouettes. It was a time when creating a role meant believing in the art rather than simply mastering the technique. The Cornejos are believers; they make the audience believe again too.