Magnetic and electron transport properties of single-crystal UPtGe

UPtGe orders below 50 K in a magnetic structure with the uranium 5f-magnetic moments arranged in a cycloid in the ac plane on a noncentrosymmetric orthorhombic crystal structure. The propagation vector q = (0.55,0,0) is directed along the a axis. There is very little magnetocrystalline anisotropy within the ac plane, compared to a large anisotropy between the two in-plane directions and the out-of-plane direction, as seen in various type of measurements. We present here results of measurements of single-crystalline magnetic susceptibility, electrical resistivity, magnetoresistivity, and thermoelectric power in order to investigate the consequences of the complex magnetic structure on the electronic behavior in UPtGe. As a result of a change in the Brillouin zone at T_N, a (pseudo)gap opens in the conduction electron band along the three principal directions. The appearance of magnetic zone boundaries due to the complex antiferromagnetic order in UPtGe is seen in the low-temperature variation of the thermoelectric power exhibiting pronounced maxima far below T_N along the three main crystallographic directions.