Complex Compounds from the Bottom of the Periodic Table

Crystallographic features play an important role in the physical and chemical properties of a given solid-state material. In particular, crystallographically complex systems exhibit a wide range of properties – from unconventional superconductivity to peculiar magnetic orders. In this talk, I will highlight some of the new complex lanthanide- and actinide-based compounds that have been discovered as part of our recent investigations [1] – [4]. A comprehensive characterization of their properties has revealed a deep interrelation between their physical and chemical features. Notably, these compounds host a large number of atoms per unit cell (111-212) and a highly coordinated environment of lanthanide/actinide atoms (14-20). The <i>R/A</i>₄Be₃₃Pt₁₆ (R = Y, La - Nd, Sm – Lu, A = Th or U) compounds crystallize in noncentrosymmetric I43d cubic space groups. While the superconducting temperatures of these materials are rather modest, their noncentrosymmetry opens a possibility of time-reversal symmetry breaking. Additionally, we have shown that it is possible to tune the ground states of these compounds by means of chemical substitution – an enhancement of superconductivity or a suppression of the magnetic order can be achieved. By studying these systems, it is possible to expand the understanding of crystal chemistry of solid-state materials, while simultaneously providing an insight into which crystallographic parameters impact the physical properties of a given solid-state material.<br/>[1] E. Svanidze <i>et al.</i>, “Empirical way for finding new uranium-based heavy-fermion materials,” <i>Phys. Rev. B</i> 99, 220403 (2019)<br/>[2] A. Amon <i>et al.</i>, “Y₄Be₃₃Pt₁₆ - a noncentrosymmetric cage superconductor with multi-centre bonding in the framework“, <i>Dalton Trans</i> 48, 9362 (2020)<br/>[3] P. Kozelj <i>et al.</i>, “A noncentrosymmetric cage superconductor Th₄Be₃₃Pt₁₆”, <i>Sci. Rep.</i> under review (2021)<br/>[4] E. Svanidze <i>et al.</i>, “Crystal structure and physical properties of novel complex noncentrosymmetric compounds <i>R</i>₄Be₃₃Pt₁₆ (<i>R</i> = Y, La-Nd, Sm-Lu)” <i>Phys. Rev. Mat.</i> 5, 074801 (2021)