Topological insulators which are insulating in the bulk yet conducting on thesurface, and gapless Dirac and Weyl semimetals, where the chiral excitations ofthe latter are manifestations of Weyl fermions, have been extensively studiedin systems without the significant influence of electron-electron interactions.However, in topological Kondo insulators, the electronic interactions induce ahybridization gap, leading to an insulating state with non-trivial topology. Itis therefore of interest to examine the fate and nature of Weyl fermions in thepresence of similarly strong electronic correlations. Here, we reportcalorimetric and magnetoresistivity measurements on the canonical heavy fermionsemimetal YbPtBi. Between 20 K and 170 K, the existence of Weyl fermions isdemonstrated by the presence of a chiral anomaly. However when the electroniccorrelations become stronger upon decreasing the temperature, the chiralanomaly contribution to the magnetoresistance becomes negligible, yet thespecific heat gives thermodynamic evidence for Weyl nodes. These resultssuggest that YbPtBi is a Weyl heavy fermion semimetal, where the bands hostingWeyl points are renormalized due to the Kondo interaction. Our findings open upthe opportunity to explore the interplay between topology and strong electroniccorrelations, when the material is tuned through a quantum critical point.
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