Carter OKs a search for material on Haig

President Carter, in an apparent administration about-face, is authorizing a search of the National Archives for White House tapes and documents relating to Alexander M. Haig Jr., an aide says. The materials are sought by some members of the Senate Foreign Relations Committee for use in hearings on Mr. Haig's confirmation as Ronald Reagan's secretary of state. Senate confirmation is likely to be stormy because of Mr. Haig's role as Richard Nixon's chief of staff during part of the Watergate scandal. The hearings, opening Friday, are expected to touch on his connection with Watergate, the Nixon pardon, and the bombing of Cambodia.