National Academy of Sciences, Proceedings of the National Academy of Sciences, 48(117), p. 30220-30227, 2020
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Significance The interplay of band-formation and electron-correlation effects in uranium heavy fermion compounds is the subject of an ongoing debate. Here unexpected insight has been gained from advanced spectroscopies on isostructural members of the U M 2 S i 2 family with different properties. The antiferromagnetic ( M = Pd,Ni), hidden order ( M = Ru), and Pauli-paramagnetic ( M = Fe) compounds all exhibit atomic-like U 5 f 2 multiplet states with singlet–singlet (quasi-doublet) symmetry while the U 5 f 3 weight increases from Pd → Ni → Ru → Fe, indicating increasing itineracy. This reveals the dual nature of the U-5 f electrons throughout the family; the local aspects persist in the hidden-order compound U R u 2 S i 2 and surprisingly even in the highly itinerant Pauli paramagnet U F e 2 S i 2 . This study gives guidelines for the theoretical treatment of U intermetallic systems.