Inelastic neutron scattering experiments have been carried out to determine the crystal-field states of the Kondo lattice heavy fermions ${\mathrm{CeRuSn}}_3$ and ${\mathrm{CeRhSn}}_3$. Both the compounds crystallize in ${\mathrm{LaRuSn}}_3$-type cubic structure (space group $Pm\overline{3}n$) in which the Ce atoms occupy two distinct crystallographic sites with cubic $\left(m\overline{3}\right)$ and tetragonal $\left(\overline{4}m.2\right)$ point symmetries. The INS data of ${\mathrm{CeRuSn}}_3$ reveal the presence of a broad excitation centered around 6–8 meV, which is accounted by a model based on crystal electric field (CEF) excitations. On the other hand, the INS data of isostructural ${\mathrm{CeRhSn}}_3$ reveal three CEF excitations around 7.0, 12.2, and 37.2 meV. The neutron intensity sum rule indicates that the Ce ions at both cubic and tetragonal Ce sites are in ${\mathrm{Ce}}^{3+}$ state in both ${\mathrm{CeRuSn}}_3$ and ${\mathrm{CeRhSn}}_3$. The CEF level schemes for both the compounds are deduced. We estimate the Kondo temperature $T_{\mathrm{K}}=3.1\left(2\right)$ K for ${\mathrm{CeRuSn}}_3$ from neutron quasielastic linewidth in excellent agreement with that determined from the scaling of magnetoresistance which gives $T_{\mathrm{K}}=3.2\left(1\right)$ K. For ${\mathrm{CeRhSn}}_3$, the neutron quasielastic linewidth gives $T_{\mathrm{K}}\approx 4.6$ K. For both ${\mathrm{CeRuSn}}_3$ and ${\mathrm{CeRhSn}}_3$, the ground state of ${\mathrm{Ce}}^{3+}$ turns out to be a quartet for the cubic site and a doublet for the tetragonal site.

• Received 3 February 2016
• Revised 28 June 2016

DOI:https://doi.org/10.1103/PhysRevB.94.014440