In 2019, unconventional superconductivity was observed in the heavy-fermion paramagnet UTe2 and a spin-triplet nature of the superconducting pairing has been proposed for this compound initially presented as a nearly-ferromagnet [1,2]. Soon after, multiple superconducting phases were found to develop near magnetic transitions in UTe2 under intense magnetic fields and high pressures [3-8].
Here, I will present a selection of results performed within a French-Japanese collaboration on UTe2. Experiments under combined extreme conditions showed that multiple superconducting phases can be induced by a magnetic field, sometimes coupled with pressure, in the vicinity of metamagnetic transitions [4,6,8] (see also [5,7]). From inelastic neutron scattering at zero magnetic field, we evidenced the presence of quasi-two-dimensional antiferromagnetic fluctuations in UTe2, which is also a two-legs magnetic ladder  (see also [10,11]). Their gapping in the zero-field superconducting phase indicates that these fluctuations may play a role in the superconducting mechanism [12-13].
Neutron scattering is a unique tool to microscopically unravel the role of magnetism, and particularly of the magnetic fluctuations, for the development of unconventional superconductivity in correlated-electrons materials. However, metamagnetism in UTe2 occurs at fields far beyond what is feasible today for inelastic neutron scattering (fields up to 36 T at ambient pressure, or up to 15-20 T under pressure may be needed). As perspectives, I will discuss how the extension of neutron techniques to higher magnetic fields, possibly coupled with very low temperatures and/or high pressures, will constitute a milestone to understand the interplay between magnetism and superconductivity in materials as UTe2.
 Ran et al., Science 365, 684 (2019).
 Aoki et al., J. Phys. Soc. Jpn. 88, 043702 (2019).
 Braithwaite et al., Commun. Phys. 2, 147 (2019).
 Knebel et al., J. Phys. Soc. Jpn. 88, 063707 (2019).
 Ran et al., Nat. Phys. 15, 1250 (2019).
 Knafo et al., Commun. Phys. 4, 40 (2021).
 Aoki et al., J. Phys. Soc. Jpn. 89, 053705 (2020).
 Valiska et al., Phys. Rev. B 104, 214507 (2021).
 Knafo et al., Phys. Rev. B 104, L100409 (2021).
 Duan et al., Phys. Rev. Lett. 125, 237003 (2020).
 Butch et al., npj Quantum Materials 7, 39 (2022).
 Duan et al., Nature 600, 636 (2021).
 Raymond et al., J. Phys. Soc. Jpn. 90, 113706 (2021).