  In a Kondo lattice system, suppression of effective Kondo coupling leads to
the breakdown of the heavy-electron metal and a change in the electronic
structure. Spin triplet superconductivity in the Kondo lattice UTe2 appears to
be associated with spin fluctuations originating from incipient ferromagnetic
order. Here we show clear evidence of twofold enhancement of spin-triplet
superconductivity near the pressure-driven suppression of the Kondo coherence,
implying that superconductivity is strengthened by the affiliated growth of
both spin and charge fluctuations. The coherent Kondo state discontinuously
transitions to ferromagnetic order at higher pressures. Application of magnetic
field tunes the system back across a first-order phase boundary. Straddling
this phase boundary, we find another example of reentrant superconductivity in
UTe2. In addition to spin fluctuations associated with ferromagnetism, our
results show that a Kondo-driven Fermi surface instability may be playing a
role in stabilizing spin triplet superconductivity.
