Magnetic structure of the antiferromagnetic half-Heusler compound NdBiPt

We present results of single-crystal neutron-diffraction experiments on the rare-earth, half-Heusler antiferromagnet (AFM) NdBiPt. This compound exhibits an AFM phase transition at T-N = 2.18 K with an ordered moment of 1.78(9) mu(B) per Nd atom. The magnetic moments are aligned along the [001] direction, arranged in a type-I AFM structure with ferromagnetic planes, alternating antiferromagnetically along a propagation vector tau of (100). The RBiPt (R = Ce-Lu) family of materials has been proposed as candidates for a new family of antiferromagnetic topological insulators (AFTIs) with a magnetic space group that corresponds to a type-II AFM structure where ferromagnetic sheets are stacked along the space diagonal. The resolved structure makes it unlikely that NdBiPt qualifies as an AFTI.