Field-dependent Hall effect in single-crystal heavy-fermion YbAgGe below 1 K

We report the results of a low-temperature (T⩾50 mK) and high-field (H⩽180 kOe) study of the Hall resistivity in single crystals of YbAgGe, a heavy-fermion compound that demonstrates field-induced non-Fermi-liquid behavior near its field-induced quantum critical point. Distinct features in the anisotropic, field-dependent Hall resistivity sharpen on cooling down and at the base temperature are close to the respective critical fields for the field-induced quantum critical point. The field range of the non-Fermi-liquid region decreases on cooling but remains finite at the base temperature with no indication of its conversion to a point for T→0. At the base temperature, the functional form of the field-dependent Hall coefficient is field-direction-dependent and complex beyond existing simple models, thus reflecting the multicomponent Fermi surface of the material and its nontrivial modification at the quantum critical point.