Magnetic signatures of multicomponent superconductivity in pressurized UTe2

The heavy fermion material UTe₂ possesses a rich phase diagram with multiple superconducting phases, several of which exhibit characteristics of odd-parity pairing. Here, we report on the pressure dependence of signatures of the superconducting transition in the temperature dependent ac magnetic susceptibility χ(T) in high quality UTe₂ single crystals. We resolve a single superconducting transition in χ(T) at low pressures $<$ 0.3 GPa. At higher pressure, however, a second feature emerges in χ(T), which is located at the thermodynamic phase boundary between two separate superconducting states previously identified by specific heat studies. The observation of a two-step transition in χ(T) can be understood as a consequence of the change in the London penetration depth, when UTe₂ switches from one superconducting phase into another.