${\mathrm{CeOs}}_2{\mathrm{Al}}_{10}$ exhibits Kondo semiconducting properties, yet orders antiferromagnetically at a rather high temperature, $T_{\mathrm{N}}=28.5$ K. We have performed break-junction tunneling measurements on single crystals of ${\mathrm{CeOs}}_2{\mathrm{Al}}_{10}$ and the nonmagnetic Kondo semiconductor ${\mathrm{CeFe}}_2{\mathrm{Al}}_{10}$. Upon cooling ${\mathrm{CeFe}}_2{\mathrm{Al}}_{10}$, two hybridization gaps successively appear in the tunneling spectra, while another gap opens in ${\mathrm{CeOs}}_2{\mathrm{Al}}_{10}$ below $T_{\mathrm{N}}$. For both compounds, the ratio of the two hybridization gap widths is approximately 4, in agreement with the hybridization gap model for the crystal-field ground state of ${\mathrm{Ce}}^{3+}$ with $|J_z\rangle =|\pm 3/2\rangle$. Furthermore, we found that the gap widths are well scaled by the Kondo temperature among Ce-based Kondo semimetals/semiconductors with orthorhombic structures.

• Received 13 September 2015

DOI:https://doi.org/10.1103/PhysRevB.92.201113