Magnetic Field-Suppressed Geometrical Frustration in the Kagome Metal CoSn

Layered Kagome networks host dispersionless low-energy excitations due to phase-destructive interference. Bringing these so-called flat bands in proximity to the Fermi level enables spin fluctuations. The magnetotransport signature of these systems is underexplored. In the frustrated paramagnetic CoSn Kagome metal, we observe a directional negative magnetoresistance in contrast to other transition metal flat band systems like FeSn, PtTl, and RhPb. We attribute this to the existence of a flat band in proximity to the Fermi level, which is consistent with our ARPES and resistivity anisotropy data. We also study the effect of magnetic/nonmagnetic doping. These transport findings prototype CoSn as an exciting platform to explore frustrated quantum states in the Kagome-derived flat band systems. In this talk, a systematic transport study as well as spectroscopy results will be presented.