Public School Teachers' Pension and Retirement Fund of Chicago plans to search for a replacement for Michael J. Nehf, executive director, who is on a leave of absence until Dec. 31, when he will leave the fund, said Patricia Townsend Knazze, president of the $10.3 billion fund. Kevin Huber, CFO, was named interim executive director, she said. Mr. Nehf's contract had been renewed for one year in August, but the board decided on the change, Ms. Knazze said. Mr. Nehf is using vacation days during his leave. She would not provide further details on his departure. An executive search firm might be hired to look for candidates when the board discusses how to proceed with the search; Ms. Knazze didn't have a timetable. Mr. Nehf couldn't be reached for comment.