Jan 4 (Reuters) - Canada’s main stock index opened higher in the first trading session of the year on Monday, supported by gains in materials stocks, while upbeat factory data for December bolstered optimism around an economic recovery. * At 9:30 a.m. ET (1430 GMT), the Toronto Stock Exchange’s S&P/TSX composite index was up 150 points, or 0.86%, at 17,583.36. (Reporting by Amal S in Bengaluru)