US STOCKS-Wall St ends slightly lower after late rally
* Tumbling oil weighs on energy stocks; materials rise
* Volatile trading session saw heavy volume
* Yellen to defend Fed rate hikes in Congress
* Indexes down: Dow 0.1 pct, S&P 0.1 pct, Nasdaq 0.4 pct (Updates to close)
By Caroline Valetkevitch
Feb 9 (Reuters) - U.S. stocks ended a volatile session barely lower on Tuesday as a late-day rally led by materials and healthcare shares offset another big drop in oil prices.
Energy was the day's weakest sector, with the index falling 2.5 percent as U.S. crude settled 5.9-percent lower.
Shares of Anadarko Petroleum dropped 7 percent to $37.24. The company announced late in the session that it was cutting its dividend, preserving cash at a time when sliding oil prices have fueled losses.
Pfizer, up 1.9 percent, and Gilead, up 2.3 percent, gave the biggest boosts to the S&P 500, while the S&P health care index rose 0.7 percent, the second-best performing sector of the day after materials, up 1.2 percent. Continuación...