Transport properties of EuNi₂Ge₂ under high pressure

Transverse magnetoresistance (MR) and Hall effect have been measured for EuNi₂Ge₂ single crystals under high pressures up to 2.0 GPa. The compound undergoes a valence transition from a nearly trivalent state to a divalent state with increasing temperature above 1.6 GPa. It was found that the transverse MR of EuNi₂Ge₂ is negative at low temperatures in the nearly trivalent state, although the compound is nonmagnetic. The origin of the negative MR is discussed. In the temperature dependence of the Hall resistivity ρH, large jumps associated with the valence transition were observed at the valence transition temperature. We also examined the field-induced valence transition by the MR and ρ_H measurements. A marked change in the Hall coefficient was observed at the valence transition field. Our analyses suggest that the ordinary Hall effect plays a dominant role in the changes in ρ_H at the valence transition.