Superconductivity and magnetism in R4Be33Pt16 (R=Y, La–Nd, Sm–Lu) : A family of crystallographically complex noncentrosymmetric compounds

Crystallographically complex compounds often possess peculiar physical properties, the evolution of which can be tracked by changing one of the constituent elements at a time. We report the discovery and synthesis of isotypic ${R}_{4}{\mathrm{Be}}_{33}{\mathrm{Pt}}_{16}$ (R = Y, La--Nd, Sm--Lu) compounds, which crystallize with the noncentrosymmetric cubic space group $I\overline{4}3d$. The lattice parameters vary from $a=13.6682(4)\phantom{\rule{0.16em}{0ex}}\AA{}$ for R = La to $a=13.4366(3)\phantom{\rule{0.16em}{0ex}}\AA{}$ for R = Lu. ${R}_{4}{\mathrm{Be}}_{33}{\mathrm{Pt}}_{16}$ phases exhibit a wide range of ground states. R = Y, La, and Lu analogs display superconductivity. Their calculated electronic structures show nonzero density of states at the Fermi level, with the value of the Sommerfeld coefficient consistent with those obtained experimentally. The rest of the ${R}_{4}{\mathrm{Be}}_{33}{\mathrm{Pt}}_{16}$ compounds exhibit magnetic ground states with ordering temperatures ranging from ${T}_{\text{mag}}=0.4$ K (R = Yb) to ${T}_{\text{mag}}=40$ K (R = Pr). The diversity of physical properties of ${R}_{4}{\mathrm{Be}}_{33}{\mathrm{Pt}}_{16}$ compounds can likely be attributed to the nature of the individual rare-earth elements, structural noncentrosymmetry, the large number of atoms per unit cell (212), as well as the complex multicenter interactions within the Be-Pt framework.