Pressure Dependence of the Magnetization in the Ferromagnetic SuperconductorUGe2

We report measurements of the pressure dependence of the low-temperature magnetization that show that the two pressure induced magnetic transitions in $\mathrm{U}\mathrm{G}{\mathrm{e}}_{\mathrm{2}}$ are of first order. Further, the pressure dependence of the uniform susceptibility relative to the superconducting transition is not as expected if the latter is driven by the proximity to a ferromagnetic quantum critical point. Our data instead suggest that the superconducting pairing could be associated with a sharp spike in the electronic density of states that is also responsible for the lower pressure magnetic transition.