  Topological materials ranging from topological insulators to Weyl and Dirac
semimetals form one of the most exciting current fields in condensed-matter
research. Many half-Heusler compounds, RPtBi (R= rare earth) have been
theoretically predicted to be topological semimetals. Among various topological
attributes envisaged in RPtBi, topological surface states, chiral anomaly and
planar Hall effect have been observed experimentally. Here, we report on an
unusual intrinsic anomalous Hall effect (AHE) in the antiferromagnetic Heusler
Weyl semimetal compounds GdPtBi and NdPtBi that is observed over a wide
temperature range. In particular, GdPtBi exhibits an anomalous Hall
conductivity of up to 60 ohm-1cm-1 and an anomalous Hall angle as large as 23%.
Muon spin resonance (mu-SR) studies of GdPtBi indicate a sharp
antiferromagnetic transition (T_N) at 9 K without any noticeable magnetic
correlations above T_N. Our studies indicate that Weyl points in these
half-Heuslers are induced by a magnetic field via exchange-splitting of the
electronic bands at or near to the Fermi energy which is the source of the
chiral anomaly and the AHE.
