High-field specific heats ofA15V3Si andNb3Sn

In order to further understand the anomalous behavior of the specific heat of ${\mathrm{Nb}}_3$Sn in an 18-T magnetic field discovered by Stewart, Cort, and Webb [Phys. Rev. B 24, 3841 (1981)], we have performed specific-heat measurements on a different sample of ${\mathrm{Nb}}_3$Sn at lower fields both in the normal and mixed states, as well as measurement to 19 T on both transforming and nontransforming ${\mathrm{V}}_3$Si. The high-field data for ${\mathrm{V}}_3$Si indicate that this material behaves quite normally, and that ${\gamma }^{\mathrm{trans}}<{\gamma }^{\mathrm{nontrans}}$, in agreement with a recent analysis by Junod and Muller [Solid State Commun. 36, 721 (1980)]. ${\mathrm{Nb}}_3$Sn, however, remains anomalous, with both the same "kink" in the normal-state field data as observed by Stewart, Cort, and Webb (although at a slightly higher temperature) and unusual mixed-state behavior. The mixed-state specific heat of the ${\mathrm{V}}_3$Si samples is as expected, based on earlier work on the mixed-state specific heat of V and Nb.