We report a new compound, Y₄RuGe₈, with a transition metal vacancy-ordered CeNiSi₂-type superstructure, which has a superconducting transition at 1.3 K. Y₄RuGe₈ crystals were grown by indium flux at relatively low temperatures (below 1273 K), which makes it possible to stabilize such a vacancy-ordered phase. The crystal structure of Y₄RuGe₈ was solved by single-crystal X-ray diffraction and confirmed by transmission electron microscopy. The as-grown Y₄RuGe₈ crystals are always twinned, crystallizing in the space group P1̅ (no. 2) with the lattice parameters a = 5.7680(1) Å, b = 8.2042(2) Å, c = 11.5093(3) Å, α = 79.696(1)°, β = 88.491(1)°, and γ = 79.637(2)°; this structure is a superstructure deriving from the higher symmetry CeNiSi₂-type structure (Cmcm, no. 63) due to the ordering of Ru vacancies. The ordering of Ru sites breaks slightly distorted Ge planes in the CeNiSi₂ prototype into infinite cis–trans Ge chains in Y₄RuGe₈. The presence of bulk superconductivity in Y₄RuGe₈ is well supported by zero resistance and a jump in specific heat at the critical transition temperature. The Sommerfeld coefficient (19 mJ K^–2 mol^–1) of the specific heat is greater than that (11 mJ K^–2 mol^–1) estimated using the bare density of states (4.7 states/eV/f.u.) from first-principles calculations. The ab initio calculations indicate that 4d electrons of both Y and Ru and 4p electrons of Ge are the main contributors to the total density of states at the Fermi level in Y₄RuGe₈.

中文翻译：

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具有空位有序 CeNiSi2 型超结构的 Y4RuGe8 中的超导性

我们报告了一种新化合物 Y ₄ RuGe ₈，它具有过渡金属空位有序的 CeNiSi ₂型超结构，在 1.3 K 下具有超导转变。 Y ₄ RuGe ₈晶体是在相对较低的温度下（低于 1273 K)，这使得稳定这种空位有序相成为可能。Y ₄ RuGe ₈的晶体结构通过单晶X射线衍射解析并通过透射电子显微镜确认。生长的 Y ₄ RuGe ₈晶体总是孪晶，在空间群P 1̅ (no. 2) 中结晶，晶格参数为a= 5.7680(1) Å，b = 8.2042(2) Å，c = 11.5093(3) Å，α = 79.696(1)°，β = 88.491(1)°，γ = 79.637(2)°；由于 Ru 空位的排序，该结构是源自更高对称性的 CeNiSi ₂型结构（Cmcm，第 63 号）的超结构。Ru位点的排序将CeNiSi ₂原型中略微扭曲的Ge平面分解为Y ₄ RuGe _{8 中的}无限顺-反Ge链。Y ₄ RuGe ₈中体超导性的存在得到零电阻和临界转变温度下比热跳跃的良好支持。索末菲系数 (19 mJ K ^–2 mol^–1 ) 的比热大于使用第一性原理计算的裸态密度 (4.7 态/eV/fu) 估计的比热 (11 mJ K ^–2 mol ^–1 )。的从头计算表明，两个Y和Ru和4P电子Ge中的4D电子是主要贡献者状态中的Y中的费米能级的总密度₄卢格₈。