Field-induced electronic correlations and superconductivity in UTe₂ beyond 40~T

Several superconducting phases have been discovered close to a metamagnetic transition in the heavy-fermion compound UTe₂, unveiling a close relation between its superconducting and magnetic properties. Although suspected to be of magnetic nature, the mechanisms stabilizing these superconducting phases remain mysterious. Here, we present electrical-resistivity measurements on UTe₂, with a current I and under pulsed magnetic fields up to 60~T rotating in the (b,c) plane. The Fermi-liquid coefficient A of the electrical resistivity reaches its maximal values at the metamagnetic transition in fields tilted by 30-40~^∘ from b to c, and it becomes asymmetric with higher values above the metamagnetic field than below. The enhancement of A is interpreted as resulting from enhanced magnetic fluctuations, in a regime which coincides with a domain of stabilization of superconductivity beyond $40$~T. These results show that the magnetic fluctuations probed here probably play a key role in stabilizing high-field superconductivity in UTe₂ and may provide further insight into the superconducting mechanisms.