SIGN REVERSAL OF THE HALL RESISTIVITY IN AMORPHOUS MO3SI

We observe a sip reversal in the Hall resistivity rho(xy) of the conve ntional superconductor amorphous (a) Mo3Si. In the Ohmic regime, rho(x y) is qualitatively similar to that observed in the high-T(c) supercon ductors. It changes sign near T(c), and the sign change persists until both rho(xy) and rho(xx) become immeasurably small at T approximately 0.8T(c)(H). At current densities above the depinning current density, the Hall anomaly persists at low temperatures T approximately 0.2T(c) (H). This is contrary to a theory by Ferrell which attributes the anom aly to the backflow of thermally excited quasiparticles. In addition a model proposed by Harris, Ong, and Yan explains the anomaly as an eff ect arising from the layered nature of the high-T(c) cuprates. This mo del, however, does not explain the anomaly in a-Mo3Si which is an isot ropic unlayered material.