We report on measurements of the in-plane transverse magnetoresistance (MR) of the Kagome superconductor CsV₃Sb₅. The MR approaches 200 % at 1.8 K and in c-axis fields of 8.5 T. The observation of quantum oscillations in fields as low as 5 T underlines the high quality of the samples. At low temperatures, the MR is unusual: it displays a quadratic field dependence in fields less than ~1 kOe, followed by a linear dependence. In the field range of 15-40 kOe, the linear dependence gives way to a downwards curvature. Above 50 kOe the dependence becomes linear again but with smaller slope.  At temperatures above 100 K, the MR is very small, <0.3 %, and quadratic. In fact, the MR and its low-field features disappear sharply at the CDW transition temperature of 95 K, suggesting that it is associated with the reconstructed Fermi surface arising due to CDW order. Our analysis indicates that the observed MR features are caused by a star-shaped Fermi surface sheet around the G point of the reconstructed Brillouin zone.

This work was supported by the U. S. Department of Energy, Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division