Results are reported for the $f$-electron intermetallic ${\mathrm{CeAuAl}}_4{\mathrm{Ge}}_2$, where the atomic arrangement of the cerium ions creates the conditions for possible geometric frustration. The magnetic susceptibility follows a Curie-Weiss temperature dependence at elevated temperatures, revealing that the cerium ions are trivalent. At lower temperatures the crystal electric field splits the Hund's rule multiplet, resulting in a weak low-temperature magnetic exchange interaction and ordering near $T_M\approx 1.4\mathrm{K}$. This occurs within a metallic Kondo lattice, where electrical resistivity and heat capacity measurements show that the Kondo-driven electronic correlations are negligible. Quantum oscillations are detected in ac-magnetic susceptibility measurements and uncover small charge carrier effective masses. Electronic structure calculations reveal that inclusion of an on-$f$-site Coulomb repulsion (Hubbard) $U$ results in antiferromagnetic order and causes the $f$-electron bands to move away from the Fermi level, resulting in electronic behavior that is dominated by the $s,p$, and $d$ bands, which are all characterized by light electron masses. Thus, ${\mathrm{CeAuAl}}_4{\mathrm{Ge}}_2$ may provide a starting point for investigating geometric magnetic frustration in a cerium lattice without strong Kondo hybridization, where calculations provide useful guidance.

• Received 19 May 2017

DOI:https://doi.org/10.1103/PhysRevMaterials.1.044404