Anomalous resistivity behavior in singlet-ground-state systems

Abstract

We present data showing that an anomalous maximum in the electrical-resistivity-versus-temperature [$\ensuremath{\rho}(T)$] curve, similar to that in ${\mathrm{Pr}}_{c}{\mathrm{La}}_{1\ensuremath{-}c}{\mathrm{Sn}}_{3}$, is present for all $c$ in ${\mathrm{Tb}}_{c}{\mathrm{Y}}_{1\ensuremath{-}c}\mathrm{As}$, but is absent for all $c$ in ${\mathrm{Tb}}_{c}{\mathrm{Y}}_{1\ensuremath{-}c}\mathrm{P}$ and ${\mathrm{Tb}}_{c}{\mathrm{Y}}_{1\ensuremath{-}c}\mathrm{Sb}$. An interesting question is why there is no maximum in $\ensuremath{\rho}(T)$ for both ${\mathrm{Tb}}_{c}{\mathrm{Y}}_{1\ensuremath{-}c}\mathrm{P}$ and ${\mathrm{Tb}}_{c}{\mathrm{Y}}_{1\ensuremath{-}c}\mathrm{Sb}$ for any $c$, while there is a maximum for all $c$ in ${\mathrm{Tb}}_{c}{\mathrm{Y}}_{1\ensuremath{-}c}\mathrm{As}$. This question is particularly striking since the crystal-field splitting and N\'eel temperature of TbP and TbSb bracket that of TbAs.