Magnetic-Field-Induced Localization Transition in HgCdTe

We have performed magnetoresistance and Hall-resistance measurements on low-carrier-concentration n-type samples of Hg_(0.76)Cd_(0.24)Te at millikelvin temperatures. We observe an abrupt rise in the Hall resistance and magnetoresistance at a characteristic field H_c which is a significant function of temperature and which allows us to reject magnetic freezeout or localization by disorder as possible mechanisms. We believe our data provide compelling evidence for a model where the magnetic field induces localization of the electrons into a three-dimensional Wigner lattice