Evidence of Fermi-Surface Reconstruction at the Metamagnetic Transition of the Strongly Correlated Superconductor UTe2

Thermoelectric power ($S$) and Hall effect ($R_{\mathrm{H}}$) measurements on the paramagnetic superconductor UTe${}_2$ with magnetic field applied along the hard magnetization $b$-axis are reported. The first order nature of the metamagnetic transition at $H_{\mathrm{m}}=H_{\mathrm{c}2}^b=35$~T leads to drastic consequences on $S$ and $R_{\mathrm{H}}$. In contrast to the field dependence of the specific heat in the normal state through $H_{\mathrm{m}}$, $S(H)$ is not symmetric with respect to $H_{\mathrm{m}}$. This implies a strong interplay between ferromagnetic (FM) fluctuations and a Fermi-surface reconstruction at $H_{\mathrm{m}}$. $R_{\mathrm{H}}$ is very well described by incoherent skew scattering above the coherence temperature $T_{\mathrm{m}}$ corresponding roughly to the temperature of the maximum in the susceptibility $T_{{\chi }_{\mathrm{m}\mathrm{a}\mathrm{x}}}$ and coherent skew scattering at lower temperatures. The discontinuous field dependence of both, $S(H)$ and the ordinary Hall coefficient $R_0$, at $H_{\mathrm{m}}$ and at low temperature, provides evidence of a change in the band structure at the Fermi level.