Upper critical fields, $H_{c2\mathrm{}}\mathrm{}\left(T\right)\mathrm{}$, and residual resistivities, ${\rho }_0$, of ${\mathrm{Nb}}_3{\mathrm{Ge}}_{1-x}{\mathrm{Sn}}_x$ pseudobinaries with $0<~x<~1$ produced by chemical vapor deposition were measured in fields up to 140 kG. The upper critical field $H_{c2\mathrm{}}\mathrm{}\left(0\right)\mathrm{}$ exhibits a minimum at $x\approx 0.4$. The temperature dependence of $H_{c2\mathrm{}}$ for all ternary concentrations follows the theory of dirty type-II superconductors. The coefficient of the electronic specific heat $\gamma$, the band density of states $N_b\mathrm{}\left(0\right)\mathrm{}$, and the electron-phonon coupling parameter are determined as a function of $x$ and ${\rho }_0$. Estimated electron-phonon coupling parameters suggest a high Fermi-surface average of McMillan's parameter $〈I^2〉$ for ${\mathrm{Nb}}_3$Ge.

• Received 20 November 1980

DOI:https://doi.org/10.1103/PhysRevB.23.4485