Tunneling spectroscopy on the correlation effects in FeSi

We have performed electron tunneling spectroscopy on FeSi single crystals i n the temperature range 4-300 K by using a scanning tunneling microscope. T he differential conductance (dl/dV), when corrected for Schottky barrier ef fects, exhibits two strongly temperature-dependent peaks on either side of the Fermi level that emerge below approximate to 200 K and that are separat ed by a (pseudo)gap of approximate to 50 meV. Our observations can be ascri bed to the formation of quasiparticle density of statics caused by d-electr on correlation. The tunneling spectra are in good agreement with photoemiss ion spectroscopy as both techniques probe the correlated d-electron density of states (DOS). Our results are also consistent with optical reflectivity data and Raman spectroscopy, which, in contrast, are sensitive to the cond uction (c) electron DOS. [S0163-1829(98)08248-4].