Magnetic-Field-Induced Phenomena in the Paramagnetic Superconductor UTe₂

We present magnetoresistivity measurements on the heavy-fermion superconductor UTe₂ in pulsed magnetic fields μ₀H up to 68~T and temperatures T from 1.4 to 80~K. Magnetic fields applied along the three crystallographic directions a (easy magnetic axis), b, and c (hard magnetic axes), are found to induce different phenomena - depending on the field direction - beyond the low-field suppression of the superconducting state. For H, a broad anomaly in the resistivity is observed at μ₀H^*10~T and $T = 1.4$~K. For H, no magnetic transition nor crossover are observed. For H, a sharp first-order-like step in the resistivity indicates a metamagnetic transition at the field μ₀Hₘ 35~T. When the temperature is raised signature of first-order metamagnetism is observed up to a critical endpoint at TCEP7~K. At higher temperatures a crossover persists up to 28~K, i.e., below the temperature T_χᵐᵃˣ = 35~K where the magnetic susceptibility is maximal. A sharp maximum in the Fermi-liquid quadratic coefficient A of the low-temperature resistivity is found at Hₘ. It indicates an enhanced effective mass associated with critical magnetic fluctuations, possibly coupled with a Fermi surface instability. Similarly to the URhGe case, we show that UTe₂ is a candidate for field-induced reentrant superconductivity in the proximity of Hₘ.