There are very few known actinide-based iron-arsenic materials, and until now, there had only been one reported uranium iron arsenide, UFeAs₂. Eteri Svanidze, Max Planck Institute for Chemical Physics of Solids, Dresden, Germany, and colleagues have discovered a second uranium iron arsenide, UFe₅As₃.

The team used a bismuth flux method to grow crystals of the new compound. They combined uranium sheets, iron powder, arsenic pieces, and bismuth granules in an alumina crucible that was then sealed in a tantalum tube. For the reaction, the tube was heated to 1150 °C. After the reaction, the bismuth flux was separated from the product by heating to 500 °C and centrifugation.

The researchers obtained UFe₅As₃ in the form of gray, needle-shaped, air-stable crystals. The compound was characterized using powder X-ray diffraction, energy-dispersive X-ray spectroscopy, and magnetic measurements. The team found that UFe₅As₃ has a monoclinic, UCr₅P₃-type crystal structure in the space group P2₁/m.  The system showed antiferromagnetic properties below 47 K, with both U and Fe atoms likely participating in the antiferromagnetic ordering.

• Discovery and Characterization of Antiferromagnetic UFe₅As₃,
  N. Zaremba, M. Krnel, Yu. Prots, M. König, L. Akselrud, Yu. Grin, E. Svanidze,
  Inorg. Chem. 2024.
  https://doi.org/10.1021/acs.inorgchem.3c03837