Dirac cones in 2D carbon allotropes are generally protected by symmorphic symmetry operations. Herein, it is proposed that TPH-graphene has Dirac cones protected by nonsymmorphic mirror symmetries. This monolayer is composed of tetragonal, pentagonal, and heptagonal carbon rings and exhibits not only good mechanical and dynamic stability but also high energetic stability. The structure has anisotropic mechanical properties, and its Young's modulus is close to that of graphene, up to 291 N m À1 . The Dirac points on high-symmetry lines ΓÀX and XÀS are protected by the nonsymmorphic mirror operations fm 010 j0, 1=2, 0g and fm 100 j0, 1=2, 0g, respectively. The edge states obtained from semi-infinite structures confirm the nontrivial topological nature of these cones. The work reveals that TPH-graphene is an excellent candidate to study nonsymmorphicsymmetry-protected Dirac cones in 2D carbon materials.

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