* TSX closes up 117.41 points, or 0.95 percent, at 12,433.53 * Materials sector leads gains amid U.S. budget uncertainty * Canpotex deal boosts potash companies By Allison Martell TORONTO, Dec 31 (Reuters) - Canada's main stock index ended the year up nearly 1 percent on Monday, boosted by the materials sector, as U.S. lawmakers neared a last-minute agreement to avoid the "fiscal cliff" that could push the U.S. economy into recession. Gold rallied in the afternoon after new