Crossover between SC states in an unconventional superconductor UCoGe   driven by ferromagnetic spin fluctuations
  UCoGe is reported as a weak ferromagnetic (FM) two-band superconductor (SC) with the critical temperature, $T_{\mathrm{SC}}\sim$ 0.7 K and the Curie temperature, $T_{\mathrm{C}}\sim$ 3 K at ambient pressure. We report exotic attributes of the SC and FM state in moderate magnetic fields. The observed phenomena clearly demonstrate that the SC regime is superior to the paramagnetic state in the vicinity of $T_{\mathrm{SC}}$. Above $T_{\mathrm{SC}}$, the zero-field state is characterized by a regime with strong FM spin fluctuations, suggesting proximity of the FM quantum critical point (FM-QCP). In addition, we observed that the robust SC regime develops independently on the existence or lack of the long-range FM ordering. 
J. Poltierov\'a Vejpravov\'a, J. Posp\'i\v{s}il, and V. Sechovsk\'y