It is pointed out that localization effects on bulk superconductivity do exist and can be significant in homogeneous amorphous alloys (or typical metallic glasses) whose upper critical fields appear to follow the standard Werthamer-Helfand-Hohenberg-Maki (WHHM) curves. Owing to the similarity in the temperature dependence of critical fields predicted by the Fukuyama-Ebisawa-Maekawa theory of the weakly localized regime and the WHHM results over a very wide temperature range, these effects have escaped notice heretofore. Comparison of the electronic density of states obtained from specific-heat measurement (absence of field-induced delocalization effects) and the ‘‘apparent’’ one derived from fitting critical-field data reveals the aforementioned effects.

• Received 26 December 1984

DOI:https://doi.org/10.1103/PhysRevB.31.7442