Magnetic-field and pressure dependence of low-temperature resistivity inUGe2

We report measurements of resistivity $\ensuremath{\rho}$ in ${\mathrm{UGe}}_{2}$ at temperatures $T$ down to $0.3\phantom{\rule{0.3em}{0ex}}\mathrm{K}$, pressures $P$ up to $19.8\phantom{\rule{0.3em}{0ex}}\mathrm{kbar}$, and magnetic fields ${B}_{\mathrm{appl}}$ up to $17.5\phantom{\rule{0.3em}{0ex}}\mathrm{T}$ applied along the magnetic easy $a$ axis. The coefficient $A$ of the ${T}^{2}$ term of $\ensuremath{\rho}(T)$ is determined as a function of ${B}_{\mathrm{appl}}$ and $P$. In the large-moment ferromagnetic phase (the $\mathrm{low}\text{\ensuremath{-}}P∕\mathrm{high}\text{\ensuremath{-}}{B}_{\mathrm{appl}}$ phase), $A$ is found to be a function of the single parameter $({B}_{\mathrm{appl}}\ensuremath{-}{B}_{x})$ and approximately obeys a power law $A\ensuremath{\propto}({B}_{\mathrm{appl}}\ensuremath{-}{B}_{x}{)}^{\ensuremath{-}1∕2}$, where ${B}_{x}$ is the transition field from the small- to the large-moment ferromagnetic phase. The $T$ dependence of $\ensuremath{\rho}$ at fields just above ${B}_{x}$ suggests a contribution to $\ensuremath{\rho}$ from excitations with a gapped spectrum.