Kondo destruction in a quantum paramagnet with magnetic frustration

We report results of isothermal magnetotransport and susceptibility measurements at elevated magnetic fields B down to very low temperatures T on single crystals of the frustrated Kondo-lattice system CePdAl. They reveal a B∗(T) line within the paramagnetic part of the phase diagram. This line denotes a thermally broadened “small”–to-“large” Fermi-surface crossover which substantially narrows upon cooling. At B0∗=B∗(T=0)=(4.6±0.1)T, this B∗(T) line merges with two other crossover lines, viz. Tp(B) below and TFL(B) above B0∗. Tp characterizes a frustration-dominated spin-liquid state, while TFL is the Fermi-liquid temperature associated with the lattice Kondo effect. Non-Fermi-liquid phenomena which are commonly observed near a “Kondo-destruction” quantum-critical point cannot be resolved in CePdAl. Our observations reveal a rare case where Kondo coupling, frustration, and quantum criticality are closely intertwined