Iron-based heavy quasiparticles in SrFe4Sb12 : An infrared spectroscopic study

should exhibit similar physical proper-ties to those of other transition-metal compounds as well asheavy fermion compounds.The hybridization of the charge carriers to the localizedmagnetic moments forms heavy quasiparticles, which iscalled “Kondo effect.” In optical spectra, a renormalizedDrude absorption due to these heavy quasiparticles is ob-served. In heavy fermions and other transition-metal com-pounds mentioned above, the enhancement in the opticalconductivity at =0 eV coherent peak and a peakat higher energy incoherent peak increase at low tempera-tures despite the fact that Drude curves for metals usuallyappear at high temperatures. Such a change in has beenobserved in MnSi Ref. 15 and Sr