# Fermi-Surface Instabilities in the Heavy-Fermion Superconductor UTe2

## TL;DR

This study investigates Fermi-surface instabilities in the heavy-fermion superconductor UTe2 through high-field transport measurements, revealing field-induced Fermi surface changes linked to magnetic polarization and strong electronic correlations.

## Contribution

It provides experimental evidence of field-induced Fermi surface instabilities in UTe2 and connects these to magnetic polarization and electronic correlations, advancing understanding of its complex electronic behavior.

## Key findings

- Fermi surface instabilities occur at specific magnetic fields and polarizations.
- Superconductivity develops in a Fermi liquid regime above 1.5 K.
- Charge carrier estimates suggest a strongly correlated metallic ground state.

## Abstract

We present different transport measurements up to fields of 29~T in the recently discovered heavy-fermion superconductor UTe$_{2}$ with magnetic field $H$ applied along the easy magnetization a-axis of the body-centered orthorhombic structure. The thermoelectric power varies linearly with temperature above the superconducting transition, $T_{SC}= 1.5$ K, indicating that superconductivity develops in a Fermi liquid regime. As a function of field the thermolelectric power shows successive anomalies which are attributed to field-induced Fermi surface instabilities. These Fermi-surface instabilities appear at critical values of the magnetic polarization. Remarkably, the lowest magnetic field instability for $H\parallel a$ occurs for the same critical value of the magnetization (0.4 $\mu_B$) than the first order metamagnetic transition at 35~T for field applied along the $b$-axis. The estimated number of charge carriers at low temperature reveals a metallic ground state distinct from LDA calculations indicating that strong electronic correlations are a major issue in this compound.