TIAA-CREF is searching for a CIO to oversee its $290 billion in assets. Martin L. Leibowitz, CIO and also vice chairman at the Teachers Insurance and Annuity Association-College Retirement Equities Fund, plans to retire in February. Officials haven't decided yet if they will also seek another vice chairman, a position created for Mr. Leibowitz the year he joined the organization in 1995. The heads of TIAA, which has $145 billion under management, and CREF, which has $131 billion under management, both report to the CIO. The CIO also oversees another $13 billion in TIAA-CREF assets not included in the two organizations' totals. Scott C. Evans, executive vice president, TIAA-CREF Investment Management LLC, leads CREF. John A. Somers, executive vice president, is head of TIAA Investments.