* TSX down 35.88 points, or 0.23 percent, at 15,720.70
* Six of the TSX's 10 main groups were lower
TORONTO, Feb 14 (Reuters) - Canada's main stock index dipped on Tuesday after five straight days of gains that took it to an all-time high, as the materials group lost ground and investors weighed testimony from Federal Reserve Chair Janet Yellen.
At 10:36 a.m. ET (1536 GMT), the Toronto Stock Exchange's S&P/TSX composite index was down 35.88 points, or 0.23 percent, at 15,720.70.
The Fed will probably need to raise interest rates at an upcoming meeting, Yellen said, although she flagged considerable uncertainty over economic policy under the Trump administration.
The prospect of U.S. economic stimulus has helped support stocks since the U.S. presidential election on Nov. 8. The TSX climbed 7 percent in that time, helped by a 13 percent gain for financials as bond yields climbed.
Higher bond yields reduce the value of insurance companies' liabilities and increase banks' net interest margins.
Financials reversed earlier losses on Tuesday to rise 0.1 percent, led by a 0.9 percent gain for Manulife Financial Corp to C$24.90.
But the materials group, which includes precious and base metals miners and fertilizer companies, lost 0.8 percent.
Teck Resources Ltd fell 2.5 percent to C$32.48 as copper pared some recent gains, while Goldcorp Inc retreated 1.5 percent to C$21.59.
Copper prices declined 0.7 percent to $6,062 a tonne, and gold futures rose 0.1 percent to $1,226.1 an ounce.
Six of the index's 10 main groups fell, with the utilities group sliding 1.2 percent and energy dipping 0.1 percent even as oil prices rose.
U.S. crude was up 1.1 percent to $53.50 a barrel, supported by an effort led by the Organization of the Petroleum Exporting Countries to cut output.
TMX Group Ltd gained 2.4 percent to C$73.00 after it reported better-than-expected fourth-quarter results, and its chief executive officer expressed optimism about the initial public offering pipeline.
Cameco Corp climbed 3.1 percent to C$15.82. BMO raised its rating and price target on the stock.
In domestic data, home prices rose in January as values in the hot Toronto market climbed even further and Vancouver prices picked up after three months of declines, the Teranet-National Bank Composite House Price Index showed. (Reporting by Fergal Smith; Editing by Lisa Von Ahn)