Electronic structure of UPt3 in the vicinity of the fermi energy

The optical reflectivity of UPt3 single crystals has been measured between 5 and 300 K for photon energies between 0.5 eV and 1 meV. The analysis of the low temperature data reveals heavy quasiparticles at EF with an effective mass of 250 m. Below the quasiparticle band of width 4 meV a pseudogap exists and a lowest energy interband transition peaks at 4 meV.