  Results are reported for the $f$-electron intermetallic CeAuAl$_4$Ge$_2$,
where the atomic arrangement of the cerium ions creates the conditions for
geometric frustration. Despite this, magnetic susceptibility measurements
reveal that the low temperature magnetic exchange interaction is weak,
resulting in marginally frustrated behavior and ordering near $T_{\rm{M}}$
$\approx$ 1.4 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 when the
experimentally observed antiferromagnetic exchange interaction and the
on-$f$-site Coulomb repulsion (Hubbard) U are considered, the $f$-electron
bands 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, CeAuAl$_4$Ge$_2$ provides a starting point for
investigating geometric magnetic frustration in a cerium lattice without strong
Kondo hybridization, where calculations provide useful guidance.
