  Journal ref.: J. Phys.: Condens. Matter 25, 065602 (2013): We investigated
the optical reflectivity of the heavy-fermion metal CeCu2Si2 in the energy
range 3 meV - 30 eV for temperatures between 4K - 300K. The results for the
charge dynamics indicate a behavior that is expected for the formation of a
coherent heavy quasiparticle state: Upon cooling the spectra of the optical
conductivity indicate a narrowing of the coherent response. Below temperatures
of 30 K a considerable suppression of conductivity evolves below a peak
structure at 13 meV. We assign this gap-like feature to strong electron
correlations due to the 4f-conduction electron hybridization.
