Temperature-field phase diagram of geometrically frustrated CePdAl

A rich temperature-field phase diagram has been constructed for the geometrically frustrated, Ising-like heavy-fermion compound CePdAl. In the limit of zero temperature, the magnetic field applied along the Ising axis (B parallel to c) induces a suppression of the antiferromagnetism, resulting in a sequence of phase transitions/crossovers, rather than a single critical point, in a critical region of field 3-5 T. In the lowest-temperature region, a power-law description of resistivity yields A . T-n with n > 2 for all applied fields up to at least 14 T. A quadratic-in-temperature resistivity term, however, can be extracted when assuming an additional electron-scattering channel from magnonlike excitations, with A tending to be divergent upon approaching the critical regime. Our observations suggest CePdAl to be a new playground for exotic physics arising from the competition between Kondo screening and geometrical frustration.