  The manifestation of Weyl fermions in strongly correlated electron systems is
of particular interest. We report evidence for Weyl fermions in the heavy
fermion semimetal YbPtBi from electronic structure calculations, angle-resolved
photoemission spectroscopy, magnetotransport and calorimetric measurements. At
elevated temperatures where $4f$-electrons are localized, there are triply
degenerate points, yielding Weyl nodes in applied magnetic fields. These are
revealed by a contribution from the chiral anomaly in the magnetotransport,
which at low temperatures becomes negligible due to the influence of electronic
correlations. Instead, Weyl fermions are inferred from the topological Hall
effect, which provides evidence for a Berry curvature, and a cubic temperature
dependence of the specific heat, as expected from the linear dispersion near
the Weyl nodes. The results suggest that YbPtBi is a Weyl heavy fermion
semimetal, where the Kondo interaction renormalizes the bands hosting Weyl
points. These findings open up an opportunity to explore the interplay between
topology and strong electronic correlations.
