We discuss and interpret the properties of the $\mathrm{Ce}\mathrm{Rh}{\mathrm{Sb}}_{1-x}{\mathrm{Sn}}_x$ systems in the concentration interval $0⩽x<0.2$. For $x\cong 0.13$ a quantum critical point has been observed by us recently and separates the Kondo-insulator (KI) from the metallic non-Fermi-liquid (NFL) state. We present the temperature dependence of the resistivity, the ac and dc magnetic susceptibilities, the specific heat, and the magnetization data through the critical concentration regime $x\sim 0.12–0.13$, as well as provide their discussion in terms of the transition from the nonmagnetic (Kondo-lattice) insulator to a weakly magnetic and singular non-Fermi liquid. The difference between the Kondo-lattice and the Mott-Hubbard semiconductors at temperature $T>0$ is emphasized. Also, the difference between those two types of insulating states is discussed. On the basis of the experimental results we propose a schematic phase diagram on the plane $T\text{−}x$ and demonstrate the rationale for the existence of the quantum critical point separating KI and NFL phases. Namely, we propose that the metallization of the insulating Kondo lattice in terms of the collective spin-singlet Kondo-lattice state destruction and a concomitant delocalization of the $4f$ electrons, within an effective $f$-band model of correlated electrons undergoing the phase transition to the insulating state.

• Received 3 June 2005

DOI:https://doi.org/10.1103/PhysRevB.72.155112