a, Temperature dependence of square resistance at varying electric fields at f = 2. MIT is observed near 0.49 V nm–1. Compared to the MIT at f = 1, strong effective mass divergence and the Pomeranchuk effect on the metallic side are not observed. b, Magnetoresistance at varying electric fields at 300 mK. Compared to the MIT at f = 1, magnetic-field-induced metal–insulator transition is not observed.