The electronic properties of Cerium (Ce) and ytterbium (Yb) intermetallic compounds may display a more local or more itinerant character depending on the interplay of the exchange interactions among the 4f electrons and the Kondo coupling between 4f and conduction electrons. For the more itinerant case, the materials form heavy-fermions once the Kondo effect is developed at low temperatures. Hence, a temperature variation occurs in the electronic structure that can be traced by investigating the optical conductivity (σ(ω)) spectra. Remarkably, the temperature variation in the σ(ω) spectrum is still present in the more localized case, even though the Kondo effect is strongly suppressed. Here, we clarify the local and itinerant character in the electronic structure by investigating the temperature dependence in the σ(ω) spectra of various Ce and Yb compounds with a tetragonal ThCr₂Si₂-type crystal structure. We explain the temperature change in a unified manner. Above temperatures of about 100K, the temperature dependence of the σ(ω) spectra is mainly due to the electron–phonon interaction, while the temperature dependence below is due to the Kondo effect.

铈 (Ce) 和镱 (Yb) 金属间化合物的电子特性可能显示出更局部或更流动的特征，这取决于 4 f电子之间的交换相互作用以及4 f和传导电子之间的 Kondo 耦合的相互作用。对于更流动的情况，一旦在低温下产生近藤效应，材料就会形成重费米子。因此，可以通过研究光导率 ( σ ( ω )) 光谱来追踪电子结构中的温度变化。值得注意的是，σ ( ω) 谱在更局部的情况下仍然存在，即使近藤效应被强烈抑制。在这里，我们通过研究具有四方 ThCr ₂ Si ₂型晶体结构的各种 Ce 和 Yb 化合物的σ ( ω ) 光谱中的温度依赖性来阐明电子结构中的局部和巡回特征。我们统一解释温度变化。高于约 100K 的温度，σ ( ω ) 光谱的温度依赖性主要是由于电子-声子相互作用，而低于温度的依赖性是由于近藤效应。