WASHINGTON — Businessman and philanthropist Roger Sant and his wife Vicki are giving $10 million to endow the director's position at the National Museum of Natural History and to support its research and programs, the Smithsonian Institution announced Wednesday.

Sant is a member of the Smithsonian Board of Regents and is co-founder of Arlington, Va.-based AES Corp., a global power company. The gift is being made through the Sants' foundation, the Summit Fund of Washington.

Sant says he wanted to make a gift in recognition of the museum's director, Cristian Samper, who announced in January he will step down from the museum this summer after nine years leading one of the largest and most visited museums on the National Mall. Samper will become president and CEO of the Wildlife Conservation Society in New York City.

"We have watched the museum grow and thrive under Cristian's leadership, so this gift is in thanks to him," Sant said. "But we also hope it will help attract our next director."

Smithsonian Secretary Wayne Clough called Sant's donation a "transformative gift" that will have a long-lasting impact on the museum.

Sant led the Smithsonian's governing board during the investigation and resignation of former secretary Lawrence Small over questionable spending. Samper became acting secretary of the entire museum complex after the scandal then returned to his museum post.

With the new gift, Sant has donated $35 million to the museum. He contributed $25 million between 2005 and 2008 to fund a new ocean hall and to endow a research position devoted to marine science.

Since he arrived in 2003, Samper has raised more than $294 million to enhance the museum's research and collections and to build new long-term exhibits and educational programs.

In May, energy businessman David H. Koch donated a record $35 million to build a new dinosaur hall at the museum on the National Mall, and Life Technologies Corp. pledged $3 million to develop the museum's first major exhibit on the human genome.

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