Multiple magnetic transitions, metamagnetism, and large magnetoresistance in GdAuGe single crystals*

We have synthesized the single crystals of GdAuGe using the Bi flux and investigated their physical properties using magnetic, heat capacity, and magnetotransport measurements as well as electronic band calculations. The temperature-dependent magnetic susceptibility data reveal an antiferromagnetic ground state with Neel temperature T_N = 17.2 K, which is further confirmed through electrical resistivity and heat capacity measurements. Further, we observed two field-induced metamagnetic (MM) transitions in magnetization measurements for H ∥ c in the magnetically ordered state. The transverse magnetoresistance is positive and large near the critical fields of MM transitions (MR ~169 % at 2 K and 9 T). We also observed a very large anomalous Hall conductivity ~ 1270 Ω^-1 cm^-1 at 2 K. The field temperature phase diagram of GdAuGe has multiple magnetic phase transitions, including a collinear antiferromagnetic ground state, two successive spin-flop transitions, and a polarized paramagnetic state with two field-induced anomalies. Our first-principles calculations suggest that GdAuGe is a Dirac nodal line semimetal.