Enhanced electron correlations in FeSb${}_2$

FeSb${}_2$ has been recently identified as a new model system for studying many-body renormalizations in a $d$-electron based narrow gap semiconducting system, strongly resembling FeSi. The electron-electron correlations in FeSb${}_2$ manifest themselves in a wide variety of physical properties including electrical and thermal transport, optical conductivity, magnetic susceptibility, specific heat and so on. We review some of the properties that form a set of experimental evidences revealing the crucial role of correlation effects in FeSb${}_2$. The metallic state derived from slight Te doping in FeSb${}_2$, which has large quasiparticle mass, will also be introduced.