Optical spectra of the heavy fermion uniaxial ferromagnet UGe2

We report on a detailed optical study of UGe$_{2}$ single crystalline material using infrared reflectivity and spectroscopic ellipsometry. The optical conductivity suggests the presence of a low frequency interband transition (~ 300 $cm^{-1}$) and a narrow free-carrier response with strong frequency dependence of the scattering rate and effective mass. We observe sharp changes in the low frequency mass and scattering rate below the upper ferromagnetic transition T$_{C_{1}}$. They recover their unrenormalized value above T$_{C_{1}}$ and for $\omega >$ 250 cm$^{-1}$. In contrast no sign of an anomaly is seen at T$_{C_ {2}} \sim$ 30 K, which is the lower transition of unknown nature. These observations are consistent with the weak anomaly observed at T$_{C_{2}}$ in transport and thermodynamic experiments.