Title: Kondo destruction in a quantum paramagnet with magnetic frustration,
Abstract: We report results of isothermal magnetotransport and susceptibility
measurements at elevated magnetic fields B down to very low temperatures T on
high-quality 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 B_0* = B*(T=0) = (4.6
+/- 0.1) T, this B*(T) line merges with two other crossover lines, viz. Tp(B)
below and T_FL(B) above B_0*. Tp 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 CePdAl. Our observations reveal a rare case where Kondo coupling,
frustration and quantum criticality are closely intertwined.