PHILADELPHIA -- The chairman of Temple University's physics department schemed to provide U.S. technology secrets to China in exchange for prestigious appointments for himself, federal authorities said in charging him with four counts of wire fraud.

Xi Xiaoxing, a naturalized U.S. citizen who was born in China, appeared in federal court Thursday and was released on $100,000 bond. A person answering the phone Friday at his home said he wasn't available to comment.

He faces up to 80 years in prison and a $1 million fine if convicted.

Prosecutors said the 47-year-old Xi had participated in a Chinese government program involving technology innovation before he took a sabbatical in 2002 to work with a U.S. company that developed a thin-film superconducting device containing magnesium diboride.

Superconductivity is the ability to conduct electricity without resistance. A superconducting thin film could be key to making computer circuits that work faster. Films of magnesium diboride are particularly promising for this use, and Xi helped developed a way to make them.

The name of the U.S. firm where Xi worked isn't included in the indictment.

Michele Mucellin, a spokeswoman for the U.S. attorney's office in Philadelphia, said she couldn't comment on what positions prosecutors say Xi sought out, whether he received them or what exactly the device is.

Ray Betzner, a spokesman for Temple University in Philadelphia, said Friday that Xi was being replaced as chairman of the physics department but remains a member of the faculty.

Xi was awarded a grant in 2004 from the U.S. Department of Defence to purchase the device to use for research, but prosecutors say he then "exploited it for the benefit of third parties in China, including government entities," by sharing it with the help of his post-doctoral students from China.

Xi also offered to build a world-class thin film laboratory there, according to emails detailed by prosecutors.

No one else has been charged in the case.

Xi joined Temple in 2009 and previously was a professor at Penn State University, according to his online faculty profile. He received his doctorate in physics from China's Peking University in 1987.

The charges come two days after three Chinese citizens who earned advanced degrees from the University of Southern California and three others were charged in San Francisco with stealing wireless technology from a pair of U.S. companies. They were charged with economic espionage and theft of trade secrets, offences that Xi was not charged with.

Mucellin said the two cases aren't connected.