Pressure-induced antiferromagnetism in UPt

UPt orders ferromagnetically at ambient pressure at 28 K. Upon increasing p ressure, an additional magnetic phase transition appears around 17 K. While the upper transition behaves with field as a typical paramagnetic ferromag netic transition, the lower one exhibits antiferromagnetic behavior. With p ressure both transitions shift towards lower temperatures. Around 1.5 GPa t he upper magnetic transition completely disappears and only the lower persi sts up to similar to4 GPa. The electrical resistivity measured up to 8.0 GP a shows that structural transformation occurs in UPt under pressure.