* TSX up 24.67 points, or 0.20 percent, at 12,340.79 * Materials sector leads index up amid U.S. budget uncertainty * Canpotex deal boosts potash companies By Allison Martell TORONTO, Dec 31 (Reuters) - Canada's main stock index rose on Monday, boosted by the materials sector as U.S. lawmakers pushed for a last-minute deal to avoid the "fiscal cliff". Some $600 billion in tax hikes and spending cuts that could push the U.S. economy into recession are set to start coming into effect at midnight. "Nobody really knows what's going to happen with the fiscal cliff," said David Baskin, president of Baskin Financial Services. "I'm seeing very light trading activity, so you could see some outside moves today simply because there isn't much volume going on." At 10:55 a.m. (1555 GMT), the Toronto Stock Exchange's S&P/TSX composite index was up 24.67 points, or 0.20 percent, at 12,340.79. The index was on track to end the year up about 3 percent. "If you're a Canadian and you bought the index you got killed by the commodities this year," said Baskin. "You got whacked by the gold stocks." Gold miners underperformed in 2012 as soaring operating and development costs cut into profits despite historically high gold prices. Gold miners rose on Monday, however, as the price of the precious metal edged higher. Goldcorp Inc was one of the most influential gainers in the index, rising 1.3 percent to C$35.92. Teck Resources Ltd, Canada's largest diversified miner, also pulled the index higher as upbeat Chinese manufacturing data boosted iron ore and copper prices. The stock was up 2.1 percent at C$35.81. The heavyweight materials sector rose 1.1 percent overall. Financial stocks, which have been rising and falling with the perceived chances of a U.S. budget deal in recent weeks, were down 0.21 percent in volatile trading. Canpotex Ltd, the offshore sales agency for Potash Corp of Saskatchewan, Mosaic Co and Agrium Inc said it struck a six-month agreement to supply a subsidiary of China's Sinofert Holdings Ltd. Potash Corp rose 0.9 percent to C$40.06, and Agrium was up 0.8 percent at C$98.58. The Canadian Imperial Bank of Commerce said it would pay $149.5 million to the estate of Lehman Brothers Holdings Inc to resolve litigation over a collateralized debt obligation tied to the bankruptcy of the former Wall Street bank. Shares fell 1.0 percent to C$79.75, and CIBC was the most influential negative stock in the index.