Effect of pressure on the anomalous magnetoresistance and antiferromagnetism of single crystal GdB4

Electrical resistance of single-crystalline GdB4 has been measured at high pressures and high magnetic fields. The antiferromagnetic ordering temperature TN increases with pressure at a rate 0.3 K/GPa, but the hidden transition temperature Ta is almost pressure independent. The magnitude of magnetoresistance at 4.2 K (about 6000% at 8.5 T) is not affected by applying pressures below 3 GPa. This fact suggests similar origins of the hidden transition and of the extremely large magnetoresistance.