Superconductivity of ${\mathrm{Nb}}_3$Ge

Evidence is presented to show that the maximum transition temperature of compounds with the $\beta$-W type structure ($A15\mathrm{}$) occurs at the stoichiometric composition $A_{3}B$, when $B$ is a nontransition element. The niobium-germanium $A15\mathrm{}$-type compound, which normally forms with excess Nb, has a transition temperature of 6.9°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°K. This large increase in transition temperature is attributed to a closer approach to the stoichiometric 3:1 composition.