Anomalous Electrical Resistivity and Defects inA−15Compounds

Measurements of the temperature dependence of the electrical resistivity and correlations observed with $T_c$ for ${\mathrm{V}}_3$Si, ${\mathrm{V}}_3$Ge, and $A-15\mathrm{}$ Nb-Ge show (i) the existence of a universal defect in the $A-15\mathrm{}$ superconductors which is not nonstoichiometry, (ii) a normal state anomaly also strongly influenced by the defects, and (iii) evidence that $T_c$ and the electron-phonon interactions for transport processes are ∼ 100 times more sensitive to defectproducing sample modifications in the $A-15\mathrm{}$ compounds than in Nb.