▎ 摘　　要

Doping graphene near the 1/4-filling to shift the extended flat band and van Hove singularity below EF has been highly desirable. Here we report the experimental observation of an extended flat band below EF in Li-intercalated graphene. Strong electron-phonon interaction is clearly identified by notable kinks in the band dispersion. Moreover, the evolution of the band structure upon Li intercalation shows that the extended flat band and the Kekul?? order emerge simultaneously. Our work provides opportunities for investigating flat-band-related instabilities and its interplay with the Kekul?? order.