Intermediate valence behavior is frequently observed in materials containing Ce, Yb, Eu, Sm, or Tm. In the current work, we report synthesis and characterization of Yb₂Cu₉Al₈ (Th₂Zn₁₇ structure type). Its intermediate valence behavior can be described by an excitation energy E_ex/k_B = 319 K and a spin fluctuation temperature T_sf = 60 K. The valence state of Yb is estimated to be close to 2.04 for the low‐temperature region. The valence gradually evolves to the value of 2.80 at T = 400 K. The specific heat coefficient of γ_exp = 59 mJ·mol_Yb^–1·K^–2 indicates a moderate effective mass enhancement, together with finite density of states at the Fermi level. The latter is also confirmed by the band structure calculations.

中文翻译：

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Yb2Cu9Al8的中间价行为

在包含Ce，Yb，Eu，Sm或Tm的材料中经常观察到中间价态行为。在当前的工作中，我们报告Yb ₂ Cu ₉ Al ₈（Th ₂ Zn ₁₇结构类型）的合成和表征。它的中间价态可以通过激发能E _ex / k _B = 319 K和自旋涨落温度T _sf = 60 K来描述。在低温区域，Yb的价态估计接近于2.04。在T = 400 K时，化合价逐渐演变为_2.80。γexp = 59 mJ的比热系数· mol _Yb ^–1 · K ^–2表示中等有效的质量增强，以及费米能级的有限状态密度。后者也被能带结构计算所证实。