The S&P 500 ended lower after a volatile session on Monday, with investors wrestling with uncertainty and bank stocks dropping following powerful Western sanctions against Russia as it continued its invasion of Ukraine. Helping the Nasdaq close in positive territory after opening at a loss, electric car makers Tesla and Rivian Automotive jumped 7.5 percent and 6.5 percent, respectively. Citigroup fell 4.5 percent and helped push the S&P 500 banks index down 2.35 percent as the U.S. 10-year Treasury yield slipped. The broader S&P 500 financial index dropped 1.5 percent. Global stocks slumped, the Russian rouble tanked to record lows and safe-haven assets got a boost after Western allies imposed new sanctions that limited Moscow’s ability to deploy its $630 billion foreign reserves and cut off some of its banks from the SWIFT global payments system. Russian artillery bombarded residential districts of Ukraine’s second-largest city, as Moscow’s invading forces met stiff …