Jan 27 (Reuters) - Canada’s main stock index opened lower on Wednesday, weighed down by weakness in materials and energy stocks, while investors awaited the U.S. Federal Reserve policy statement for clarity on monetary stimulus. * At 9:30 a.m. ET (1430 GMT), the Toronto Stock Exchange’s S&P/TSX composite index was down 148.67 points, or 0.84%, at 17,630.74. (Reporting by Amal S in Bengaluru; Editing by Ramakrishnan M.)