Metamagnetism in the high-pressure tetragonal phase of UTe₂

A structural orthorhombic-to-tetragonal phase transition was recently discovered in the heavy-fermion compound UTe₂ at a pressure p^*3-8~GPa [Honda et al., J. Phys. Soc. Jpn. 92, 044702 (2023); Huston et al., Phys. Rev. Mat. 6, 114801 (2022)]. In the high-pressure tetragonal phase, a phase transition at Tₓ=235~K and a superconducting transition at Tsc=2~K have been revealed. In this work, we present an electrical-resistivity study of UTe₂ in pulsed magnetic fields up to μ₀H=58~T combined with pressures up to p = 6 GPa. The field was applied in a direction tilted by 30~^∘~from b to c in the orthogonal structure, which is identified as the direction c of the tetragonal structure. In the tetragonal phase, the presence of superconductivity is confirmed and signatures of metamagnetic transitions are observed at the fields μ₀Hₓ₁=24~T and μ₀Hₓ₂=34~T and temperatures smaller than Tₓ. We discuss the effects of uniaxial pressure and we propose that a magnetic ordering drives the transition at Tₓ.