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 CePdA1. 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 B-0* = B*(T = 0) = (4.6 +/- 0.1)T, this B* (T) line merges with two other crossover lines, viz. T-p (B) below and T FL (B) above B-0*. T-p characterizes a frustration-dominated spin-liquid state, while T-FL 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 CePdA1. Our observations reveal a rare case where Kondo coupling, frustration, and quantum criticality are closely intertwined