Rare $d$-electron-derived heavy-fermion properties of the solid-solution series ${\mathrm{LaCu}}_3{\mathrm{Ru}}_x{\mathrm{Ti}}_{4-x}{\mathrm{O}}_{12}$ were studied for $1\le x\le 4$ by resistivity, susceptibility, specific-heat measurements, and magnetic-resonance techniques. Our results suggest the existence of a coherent Kondo lattice formed by localized Ru $4d$ electrons leading to strongly enhanced effective electron masses. Pure ruthenate $\left(x=4\right)$ is a heavy-fermion metal characterized by a resistivity proportional to $T^2$ at low temperatures $T$. By increasing titanium substitution the coherent Fermi-liquid state is disturbed, yielding single-ion Kondo-type properties as in the paradigm $4f$-based heavy-fermion compound ${\mathrm{Ce}}_x{\mathrm{La}}_{1-x}{\mathrm{Cu}}_{2.05}{\mathrm{Si}}_2$ [M. Ocko et al., Phys. Rev. B 64, 195106 (2001)]. In ${\mathrm{LaCu}}_3{\mathrm{Ru}}_x{\mathrm{Ti}}_{4-x}{\mathrm{O}}_{12}$ the heavy-fermion behavior finally breaks down upon crossing the metal-to-insulator transition close to $x=2$.

• Received 19 March 2015
• Revised 8 March 2016

DOI:https://doi.org/10.1103/PhysRevB.93.115149