Heavy carriers and non-Drude optical conductivity in MnSi

metals. 3 However, the high value of the reflection coefficient close to the 100% line prevented a detailed analysis of the frequency-dependent optical conductivity in this range. In this Rapid Communication, we overcome this hurdle by using p-polarized light at a grazing angle of incidence of 80°, for which the reflection coefficient drops well below the 100% line. We show that the frequency-dependent-scattering rate and the effective mass deviate from the behavior expected for Fermi liquids which can be understood from the fact that the optical conductivity is best described with an expression that departs from the usual Drude model. Single crystals were grown using the traveling floatingzone technique. 3,4 The temperature dependence of the resistivity is shown in Fig. 1. Fitting the resistivity to r(T)