Coexisting Kondo and Weyl-like transport in kagome heavy-fermion metal, Yb$_y$Co$_3$G$e_{3-x}$Sn$_x$

Abstract

Strong electron correlations and topology offer complementary routes to controlling electrical conduction, as correlations can make electrons heavy (e.g. Kondo lattices) whereas topology can make them behave as massless particles (e.g. Dirac or Weyl systems), and having both in one material is rare. In Kondo lattice systems, Kondo hybridization between localized 4$f$ and conduction electrons strongly enhances the quasiparticle mass, where in Weyl-Kondo systems these Kondo-renormalized bands form Weyl states, and simultaneous signs of both Kondo and Weyl states in one material have not been observed in transport. Here we report signs of both in the kagome metal \ce{Yb_yCo3Ge_{3-x}Sn_x} by combining magnetotransport, heat capacity, magnetization, angle-resolved and X-ray photoemission spectroscopy, and DFT+U calculations to reveal Yb-dependent Kondo scattering developing into lattice coherence, with extrapolated Sommerfeld coefficient of approximately 2 ~Jmol$_{\mathrm{Yb}}^{-1}$K$^{-2}$. Transverse magnetoresistance (MR) follows single-ion Kondo scaling, whereas longitudinal transport contains an additional negative response proportional to B$^2$ and remains unsaturated up to 32 T, consistent with a chiral anomaly. These findings support a picture of Kondo and Weyl-like conduction arising from distinct electronic states without external Fermi-level tuning, suggesting a possible route to combining correlated and topological functionality in a bulk material.