Low-temperature thermal expansion of CeBiPt

CeBiPt is a low-carrier-density semimetal which exhibits antiferromagnetic ordering below T N = 1.1 K . We measured the thermal expansivity α down to 0.3 K in zero and applied magnetic field B = 1 T . In B = 0 , a peak in α ( T ) indicates the antiferromagnetic phase transition. Antiferromagnetic ordering is suppressed in low fields. With increasing field Zeeman splitting of the ground state appears. The low-energy thermal exitations are seen as a minimum in the temperature dependence of the longitudinal thermal expansivity. The magnetostriction, i.e. the relative length change Δ L ( B ) / L ( 0 ) as a function of B, reaches a large value of 4 × 10 - 4 at B = 8 T .