Inverted structures of common crystal lattices, referred to as antistructures, are rare in nature due to their thermodynamic constraints imposed by the switched cation and anion positions in reference to the original structure. However, a stable antistructure formed with mixed bonding characters of constituent elements in unusual valence states can provide unexpected material properties. Here, a heavy-fermion behavior of ferromagnetic gadolinium lattice in Gd₃SnC antiperovskite is reported, contradicting the common belief that ferromagnetic gadolinium cannot be a heavy-fermion system due to the deep energy level of localized 4f-electrons. The specific heat shows an unusually large Sommerfeld coefficient of ≈1114 mJ mol⁻¹ K⁻² with a logarithmic behavior of non-Fermi-liquid state. It is demonstrated that the heavy-fermion behavior in the non-Fermi-liquid state appears to arise from the hybridized electronic states of gadolinium 5d-electrons participating in metallic GdGd and covalent GdC bonds. These results accentuate the unusual chemical bonds in CGd₆ octahedra with the dual characters of gadolinium 5d-electrons for the emergence of heavy fermions.

中文翻译：

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反钙钛矿 Gd3SnC：Gd 晶格中铁磁性和重费米子的异常共存

常见晶格的倒置结构（称为反结构）在自然界中很少见，因为它们的热力学限制是由相对于原始结构的转换阳离子和阴离子位置强加的。然而，具有不寻常价态的组成元素的混合键合特性形成的稳定反结构可以提供意想不到的材料特性。在这里，报道了 Gd ₃ SnC 反钙钛矿中铁磁钆晶格的重费米子行为，这与由于局部 4f 电子的深能级而导致铁磁钆不能成为重费米子系统的普遍看法相矛盾。比热显示出异常大的 Sommerfeld 系数≈ 1114 mJ mol ^-1 K ^-2具有非费米液态的对数行为。结果表明，非费米液态中的重费米子行为似乎是由参与金属 Gd  Gd 和共价 Gd  C 键的钆 5d 电子的杂化电子态引起的。这些结果强调了 CGd ₆八面体中不寻常的化学键，以及重费米子出现的钆 5d 电子的双重特性。