▎ 摘　　要

A material generally contracts transversely when stretched along one direction. A few materials exhibit unusual auxeticity, which is rarely observed in planar two-dimensional materials. Herein, a planar graphene allotrope ?-graphene with a highly negative Poisson's ratio is proposed. ?-Graphene possesses excellent mechanical properties and exhibits a unique highly negative Poisson's ratio of -0.17 along the crystallographic armchair direction, which is six times larger than that of graphene. Additionally, ?-graphene exhibits intrinsic semimetallic characteristics with a Dirac cone located at 0.08 eV below the Fermi level. In particular, the Dirac cone of ?-graphene persists throughout the entire strain range. A highly negative Poisson's ratio and semimetallic properties endow ?-graphene with excellent potential for practical application to nanomechanical and nanoelectronic devices.