The former chairman of Temple University's physics department has pleaded not guilty to charges he gave U.S. technology secrets to China.

Xi Xiaoxing (shee show-shing) is an expert on superconductivity. Federal prosecutors say he sought prestigious appointments in China in exchange for providing data on a U.S. firm's device.

The 47-year-old professor appeared in court in Philadelphia Thursday to enter his not guilty plea.

He is free on $100,000 bail but has surrendered his passport. He is a naturalized U.S. citizen born in China.

Xi has retained Washington lawyer Peter Zeidenberg, who successfully defended an Ohio woman in a Chinese spying case.

Zeidenburg vows that Xi will also be exonerated.

He remains a Temple faculty member. He lives with his wife and children in suburban Philadelphia.