Resistance minimum observed at Landau level filling factor nu=1/2 in ultra high magnetic fields

We study the magnetotransport near Landau level filling factor nu=1/2 in a gated GaAs-Al(0.3)Ga(0.7)As square quantum well (width 35 nm) in magnetic field up to 45 T and in a temperature (T) range between 50 mK and 1.5 K. The longitudinal resistance at nu=1/2, R(xx)(nu=1/2), exhibits a steep valley that is flanked by a pair of rising resistance peaks in low T. The R(xx)(nu=1/2) shows nonmonotonous dependence on T, with a minimum resistance reached at T similar to 0.5 K. The concomitant Hall resistance R(xy) is not strictly linear with magnetic field and its slope shows a sharp cusp at nu=1/2, indicating a nonclassical Hall effect. The data are characteristic for ultra high field magnetotransport around nu=1/2 in thick, but single-layer, quantum wells.