Kagome lattice systems provide a platform for a rich variety of novel quantum phases of matter, such as quantum spin liquids, Dirac/Wyle fermions, unconventional superconductivity, and charge/spin order, owing to their frustrated geometry and non-trivial topological nature. Recently, a new family of kagome superconductors AV₃Sb₅ (A = K, Rb, Cs) has attracted tremendous attention because of their unique band structure with van Hove singularities and Dirac dispersions. All the members show unconventional charge-density-wave (CDW) order with time-reversal symmetry breaking. Very interestingly, a non-monotonic Hall coefficient anomaly has been reported below T_CDW. Various possibilities, such as Berry curvature, skew scattering, and loop current, have been proposed as the origin, but it has not yet been clarified.

Here we report on magnetotransport measurements in CsV₃Sb₅. We analyzed s_xx(H) and s_xy(H) simultaneously using the μ-spectrum method, which does not require any assumptions on the carrier type and the number of bands. Our analysis suggests that there exist tiny Fermi pockets with extremely high mobility below T_CDW, which give rise to the Hall coefficient anomaly.