Superconductivity ofNb3Ge

Evidence is presented to show that the maximum transition temperature of compounds with the $\ensuremath{\beta}$-W type structure ($A15$) occurs at the stoichiometric composition ${A}_{3}B$, when $B$ is a nontransition element. The niobium-germanium $A15$-type compound, which normally forms with excess Nb, has a transition temperature of 6.9\ifmmode^\circ\else\textdegree\fi{}K. It has been found that ${\mathrm{Nb}}_{3}$Ge compounds prepared by rapid-quench techniques, in the presence of excess germanium, have transition temperatures as high as 17\ifmmode^\circ\else\textdegree\fi{}K. This large increase in transition temperature is attributed to a closer approach to the stoichiometric 3:1 composition.