Uranium-mercury complex antiferromagnet: UHg_6.4

Crystallographically complex compounds containing 4f and 5f electrons often have peculiar chemical and physical properties. In this work we present discovery and characterization of a new material UHg6.4, located at the border to complex intermetallics. This material crystallizes in the LaHg6.4 structure type, which can be represented by La/U-centered polyhedra with coordination numbers of 13 and 14. Much like the LaHg6.4 analog, UHg6.4 shows strong crystallographic disorder, in particular for Hg atoms in the channels along [001]. The UHg6.4 compound orders antiferromagnetically below TN1=35.5±1K and displays another transition at TN2=47.3±1K, which is likely also antiferromagnetic. Both transitions are only slightly affected by magnetic field. Given high air sensitivity of UHg6.4, an exceptional experimental environment for sample synthesis and characterization was necessary in order to comprehensively describe the chemical and physical properties of this system. © 2022 authors. Published by the American Physical Society. Published by the American Physical Society under the terms of the "https://creativecommons.org/licenses/by/4.0/"Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI. Open access publication funded by the Max Planck Society