Upper Critical Fields of Transition Metal Alloy Superconductors

An interpretation is presented of the persistence of superconductivity of transition metal alloys at very high magnetic fields. The interpretation is based on pulsed-magneticfield data on the low-current-density resistive critical fields of concentrated transition metal alloys, the GinsbergLandau-Abrikosov- Gor'kov theory, and a paramagnetically limited critical-field criterion. The arguments add weight to previous evidence of a negative-surface-energy picture for alloy superconductors with short electronic mean-free. path. (H.D.R.)