A study of the electronic structure of the alternating monolayer-trilayer (1313) phase of La₃Ni₂O₇ reveals significant differences compared to the previously studied bilayer (2222) structure. Using angle-resolved photoemission spectroscopy (ARPES), researchers identified a flat band with a distinct binding energy and an additional electron pocket in the 1313 structure. These findings suggest strong correlation effects, as evidenced by renormalizations of the Ni-d_{z²} and Ni-d_{x²−y²} bands, with values of about 5–7 and 4, respectively. The 1313 structure also exhibits split flat bands near the Fermi energy (E_F), with one band lying below E_F and another above. These differences in electronic structure may be crucial for understanding the high-temperature superconductivity observed in La₃Ni₂O₇ under high pressure. The study also highlights the importance of structural motifs in determining the electronic properties of nickelates, which are closely related to the cuprate family of high-temperature superconductors. The results provide a foundation for further experimental and theoretical investigations into the unique electronic properties of the 1313 structure.A study of the electronic structure of the alternating monolayer-trilayer (1313) phase of La₃Ni₂O₇ reveals significant differences compared to the previously studied bilayer (2222) structure. Using angle-resolved photoemission spectroscopy (ARPES), researchers identified a flat band with a distinct binding energy and an additional electron pocket in the 1313 structure. These findings suggest strong correlation effects, as evidenced by renormalizations of the Ni-d_{z²} and Ni-d_{x²−y²} bands, with values of about 5–7 and 4, respectively. The 1313 structure also exhibits split flat bands near the Fermi energy (E_F), with one band lying below E_F and another above. These differences in electronic structure may be crucial for understanding the high-temperature superconductivity observed in La₃Ni₂O₇ under high pressure. The study also highlights the importance of structural motifs in determining the electronic properties of nickelates, which are closely related to the cuprate family of high-temperature superconductors. The results provide a foundation for further experimental and theoretical investigations into the unique electronic properties of the 1313 structure.