Microscopic description of origin of heavy quasiparticles in ${\mathrm{UPt}}_3$

We propose a microscopic description of heavy fermions in ${\mathrm{UPt}}_3.$ It is based on the assumption that two of the three $5f$ electrons of the U ions are localized. Band-structure calculations based on this supposition reproduce the observed de Haas–van Alphen frequencies very well. The observed enhancement of the quasiparticle mass as compared with the local-density approximation band mass results from the local Coulomb interaction of the delocalized f electrons with the localized ones. Diagonalization of the Coulomb interaction matrix yields the level scheme of the localized $f^2$ states. Assuming a splitting of the ground-state doublet by the crystal field of similar size as in ${\mathrm{UPd}}_2{\mathrm{Al}}_3$ results in a mass enhancement factor of order 10 in agreement with experiments.