Weak localization in superconductors: A study of radiation-damagedNb3Ir

We have studied the critical temperature $T_c$, upper critical field, and magnetotransport variation as a function of radiation damage in the low-$T_c$ A15 superconductor ${\mathrm{Nb}}_3$Ir. We find a nonmonotonic variation in $T_c$ with disorder and analyze these results in terms of the competition between density-of-states effects and weak localization. Magnetoresistance measurements confirm the presence of electron interaction effects associated with weak localization.