| Increasing experimental evidence points towards a two-fluid model for the 5f shells in actinide-based heavy fermion compounds with some 5f electrons being localized atomic-like and others being band-like itinerant. The dual nature can explain various unusual low-energy properties of U compounds including the formation of heavy fermion and their unconventional superconductivity. The dual model, however, provides an effective Hamiltonian which is valid only for the low-energy regime. The important task is to show how this effective picture can be derived from a more microscopic description of the correlated 5f electrons. The present contribution focusses on intra-atomic correlations among the 5f electrons as a possible mechanism for orbital-selective (partial) localization. The central goal is to theoretically derive criteria and specify properties which experimentally characterize correlation-induced partial localization in actinide compounds. The theoretical ansatz is based on combining ab-initio band structure calculations with typical many-body techniques like Cluster Pertubation Theory. Results for the U-based heavy fermion superconductors UPd2Al3 will be presented emphasizing the consequences for the interpretation of experimental data. |
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