Evidence for a hybridization gap in noncentrosymmetric CeRuSi3

Inelastic neutron scattering (INS) and specific heat measurements have been performed on the intermediate valence compound CeRuSi$_3$, which is isostructural to the noncentrosymmetric pressure-induced superconductors CeRhSi$_3$, CeIrSi$_3$ and CeCoGe$_3$. INS measurements at 7~K reveal a broad peak at (58.5~$\pm$~1.4)~meV, while at 300~K, broad quasielastic scattering is observed. This indicates a large Kondo temperature of $T_{\rm K}~\sim~680$~K. The magnetic contribution to the specific heat ($C_{\rm mag}$) has a value of $\gamma~=~62.5(1)$~mJ/mol~K$^2$ at low temperatures and above about 100~K can be well accounted for by the Coqlbin-Schrieffer model with a characteristic temperature of $T_0$~=~680~K, which is further evidence that CeRuSi$_3$ is in the intermediate valence regime.