A combined study of the structural and electronic properties of polycrystalline Pu2C3 is reported based on x-ray diffraction, specific heat, magnetic susceptibility, 13C nuclear magnetic resonance (NMR), and band structure calculations. X-ray diffraction reveals a global noncentrosymmetric cubic lattice, with a nearest-neighbor C--C bond length of r=1.38 \r{A}. 13C NMR measurements indicate that the global cubic symmetry is locally broken, revealing two unique carbon environments. Magnetic susceptibility suggests enhanced Pauli paramagnetism, and specific heat reveals a moderately large electronic Sommerfeld coefficient γ=45 mJ molPu−1 K−2, with a Wilson ratio RW≈1.3 further indicating moderate correlations. 13C nuclear spin-lattice relaxation rate (1/T1) and Knight shift (K) measurements find metallic Korringa behavior (i.e., T1TK2= const.) with modest ferromagnetic spin fluctuations at low temperature. Taken together, the data point to a delocalized nature of a narrow 5f-electron band with weak electronic correlations. Density functional theory band-structure calculations confirm the appearance of such narrow 5f bands near the Fermi level. Our data provide prime evidence for a plutonium-based metallic system with weak electronic correlations, which sheds new light on the understanding of complex paramagnetism in actinide-based metallic compounds.
@article{arxiv.2506.09911,
title = {Microscopic investigation of enhanced Pauli paramagnetism in metallic Pu$_2$C$_3$},
author = {R. Yamamoto and M. S. Cook and A. R. Altenhof and P. Sherpa and S. Park and J. D. Thompson and H. E. Mason and D. C. Arellano and D. V. Prada and P. H. Tobash and F. Ronning and E. D. Bauer and N. Harrison and W. A. Phelan and A. P. Dioguardi and M. Hirata},
journal= {arXiv preprint arXiv:2506.09911},
year = {2025}
}