Temperature-dependent infrared reflectivity spectra of SrFe$_{ 4}$Sb$_{ 12}$ has been measured. A renormalized Drude peak with a heavy effective mass and a pronounced pseudogap of 10 meV develops in the optical conductivity spectra at low temperatures. As the temperature decreases below 100 K, the effective mass ($m^{ *}$) rapidly increases, and the scattering rate ($1/\tau$) is quenched. The temperature dependence of $m^{ *}$ and $1/\tau$ indicates that the hybridization between the Fe 3d spins and the charge carriers plays an important role in determining the physical properties of SrFe$_{ 4}$Sb$_{ 12}$ at low temperatures. This result is the clear evidence of the iron-based heavy quasiparticles.
Categories: cond-mat.str-el cond-mat.mtrl-sci