We have performed electron tunneling spectroscopy on FeSi single crystals in the temperature range 4–300 K by using a scanning tunneling microscope. The differential conductance $\mathrm{}(dI/dV),$ when corrected for Schottky barrier effects, exhibits two strongly temperature-dependent peaks on either side of the Fermi level that emerge below $\approx 200$ K and that are separated by a (pseudo)gap of $\approx 50$ meV. Our observations can be ascribed to the formation of quasiparticle density of states caused by d-electron correlation. The tunneling spectra are in good agreement with photoemission 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 conduction $\mathrm{}\left(c\right)\mathrm{}$ electron DOS.

• Received 22 August 1997

DOI:https://doi.org/10.1103/PhysRevB.58.15483