Anomalous electrical resistivity of the Kondo system $\mathrm{Ce}{\left({\mathrm{Rh}}_{1-x}{\mathrm{Co}}_x\right)}_3{\mathrm{B}}_2$

Electrical resistivity measurements have been carried out on the high-Curie-temperature ferromagnetic compound Ce${\mathrm{Rh}}_3$ ${\mathrm{B}}_2$ ($T_C=110\mathrm{}-115$ K). The temperature dependence of the electrical resistivity $\rho \mathrm{}\left(T\right)\mathrm{}$ during the initial cooldown above $T_C$ gives the first solid indication of the Kondo-like behavior in this system. However, the resistivity is irreversible above $T_C$ when warming up from low temperature and $\rho \mathrm{}\left(T\right)\mathrm{}$ approaches the previous reported form. This irreversibility is closely related to microscopic cracks created by the strong internal magnetic field of the ferromagnetic state and was not observed in the nonmagnetic compound Ce${\mathrm{Co}}_3$ ${\mathrm{B}}_2$ with the same hexagonal structure. Further proof of this Kondo state can be obtained in the study of the pseudoternary system $\mathrm{Ce}{\left({\mathrm{Rh}}_{1-x}{\mathrm{Co}}_x\right)}_3{\mathrm{B}}_2$ where the resistivity increases with decreasing temperature during the initial cooldown and a local minimum Kondo anomaly was observed. The magnetic state is rapidly broken up with the replacement of Rh and Co and the resistivity anomaly disappears after the disappearance of ferromagnetic order.