Sign reversal of the Hall resistivity in amorphous Mo3Si

We observe a sign reversal in the Hall resistivity ρxy of the conventional superconductor amorphous (a) Mo3Si. In the Ohmic regime, ρxy is qualitatively similar to that observed in the high-Tc superconductors. It changes sign near Tc, and the sign change persists until both ρxy and ρxx become immeasurably small at T∼0.8Tc(H). At current densities above the depinning current density, the Hall anomaly persists at low temperatures T∼0.2Tc(H). This is contrary to a theory by Ferrell which attributes the anomaly to the backflow of thermally excited quasiparticles. In addition a model proposed by Harris, Ong, and Yan explains the anomaly as an effect arising from the layered nature of the high-Tc cuprates. This model, however, does not explain the anomaly in a-Mo3Si which is an isotropic unlayered material. © 1994 The American Physical Society.