LAUSR

We study the quasiparticle spectrum in an underscreened Kondo-lattice (KL) model that involves a single spin degenerate conduction band and two crystalline-electric-field (CEF) split Kramers doublets coupled by both orbital-diagonal and nondiagonal exchange interactions. We find the three quasiparticle bands of the model using a constrained fermionic mean field approach. While two bands are similar to the one-orbital model, a new genuinely heavy band inside the main hybridization gap appears in the quasiquartet model. Its dispersion is due to effective hybridization with conduction states, but the bandwidth is controlled by the size of the CEF splitting. Furthermore, several new indirect and direct hybridization gaps may be identified. By solving the self-consistency equation, we calculate the CEF splitting and exchange dependence of effective Kondo low-energy scale, hybridization gaps, and bandwidths. We also derive the quasiparticle spectral densities and their partial orbital contributions. We suggest that the two-orbital KL model can exhibit mixed CEF/Kondo excitonic magnetism.