The Fermi surface of CeCu₂Si₂ has two pockets due to the contribution of 4f electrons.

From the article:

Revealing the Heavy Quasiparticles in the Heavy-Fermion Superconductor ${\mathrm{CeCu}}_2{\mathrm{Si}}_2$
Zhongzheng Wu, Yuan Fang, Hang Su, Wu Xie, Peng Li, Yi Wu, Yaobo Huang, Dawei Shen, Balasubramanian Thiagarajan, Johan Adell, Chao Cao, Huiqiu Yuan, Frank Steglich, and Yang Liu
Phys. Rev. Lett. 127, 067002 (2021)

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