Metamagnetism in the high-pressure tetragonal phase of UTe${}_2$

A structural orthorhombic-to-tetragonal phase transition was recently discovered in the heavy-fermion compound UTe${}_2$ at a pressure $p^{\ast }\simeq 3-8$~GPa [Honda $\mathit{\text{et}}\mathit{\text{al.}}$, J. Phys. Soc. Jpn. $\mathbf{\text{92}}$, 044702 (2023); Huston $\mathit{\text{et}}\mathit{\text{al.}}$, Phys. Rev. Mat. $\mathbf{\text{6}}$, 114801 (2022)]. In the high-pressure tetragonal phase, a phase transition at $T_x=235$~K and a superconducting transition at $T_{sc}=2$~K have been revealed. In this work, we present an electrical-resistivity study of UTe${}_2$ in pulsed magnetic fields up to ${\mu }_{0}H=58$~T combined with pressures up to $p$ = 6 GPa. The field was applied in a direction tilted by 30~${}^{\circ }$~from $\mathbf{\text{b}}$ to $\mathbf{\text{c}}$ in the orthogonal structure, which is identified as the direction $\mathbf{\text{c}}$ of the tetragonal structure. In the tetragonal phase, the presence of superconductivity is confirmed and signatures of metamagnetic transitions are observed at the fields ${\mu }_0{H}_{x1}=24$~T and ${\mu }_0{H}_{x2}=34$~T and temperatures smaller than $T_x$. We discuss the effects of uniaxial pressure and we propose that a magnetic ordering drives the transition at $T_x$.