  Time-reversal symmetry breaking (TRSB) in UTe2 was inferred from observations
of a spontaneous Kerr response in the superconducting state after cooling in
zero magnetic field, while a finite c-axis magnetic field training was further
used to determine the nature of the non-unitary composite order-parameter of
this material. Here we present an extensive study of the magnetic-field-trained
Kerr effect, which unveils a unique critical state of pinned ferromagnetic
vortices. We show that a remanent Kerr signal that appears following the
removal of a training magnetic field, which reflects the response of the TRSB
order parameter and the external magnetic field through the paramagnetic
susceptibility. This unambiguously demonstrate the importance of the
ferromagnetic fluctuations and their intimate relation to the composite order
parameter. Focusing the measurement to the center of the sample, we are able to
accurately determine the maximum field that is screened by the critical state
and the respective critical current. Measurements in the presence of magnetic
field show the tendency of the superconductor to produce shielding currents
that oppose the increase in vortex-induced magnetization due to the diverging
paramagnetic susceptibility.
