Two U.S. Senators have asked Arthur Samberg, chairman and C.E.O. of Pequot Capital Management, to turn over records relating to $2.1 million that the hedge fund has paid to an ex-employee who figured in a now-closed insider-trading investigation of Samberg.

Charles Grassley, the senior Republican on the Senate Finance Committee, and Arlen Specter, ranking Republican on the Judiciary Committee, made the demand in a letter dated December 10. That was the same day Portfolio.com first reported on the payments.

In the letter, the Senators noted that the man who received the payments, David Zilkha, "was a key figure and potential adverse witness" in the Securities and Exchange Commission investigation of Samberg, and a subsequent Senate investigation into why the S.E.C. had dropped the case.

The Senators' letter asks that Samberg turn over the records, by December 17 "in order to avoid any appearance that the payments were related to either the S.E.C. or the Senate investigations."

Samberg spokesman Jonathan Gasthalter said Sunday that the hedge fund and its chairman would comply with the Senators' demand.

"We will cooperate fully with the Senators' request," he said. "The payments made to David Zilkha are pursuant to the settlement of a civil claim related to his employment and termination by Pequot that was first presented to the firm in January 2007 after all investigations had been closed."

Records obtained in Zilkha's divorce case show that Samberg paid Zilkha $1.4 million in two installments beginning in 2007, after the S.E.C. and Senate investigations had ended, and that he has promised $700,000 more in April 2009.

Several Senators, including Grassley and Specter, have pressed the S.E.C. to reopen the case. They are looking into whether the payments may have been made in exchange for Zilkha not giving investigators adverse information about Samberg.

Pequot had hired Zilkha, a former Microsoft employee, as a securities analyst in 2001. A Samberg spokesman has said the $2.1 million in payments were related to an "employment claim" Zilkha made to Pequot in 2007.

The S.E.C. inquiry, closed with no charges filed in 2006, looked into whether Zilkha had fed Samberg inside information about Microsoft when was still working at the software company.

A separate facet of the investigation had dealt with whether Morgan Stanley C.E.O. John Mack may also have given inside information to Pequot. That investigation also ended without any charges being filed.

However, the lead S.E.C. lawyer investigating the case was fired and claimed publicly that S.E.C. officials had moved to block the case because of Mack's political ties. That sparked the Senate committees' investigation, which produced a report in 2007 harshly critical of the S.E.C.'s handling of the case.

Samberg and Mack have strongly denied that any inside information was leaked. Zilkha couldn't be located for comment, and his lawyer has declined to respond to questions from Portfolio.com.