We theoretically investigate the superconducting surface states of topological nonsymmorphic crystalline insulators with wallpaper fermions, which are surface quasiparticles protected by a wallpaper group $p4g$ symmetry, based on a tight-binding model for the space group $P4/mbm$ (No. 127). A symmetry-based analysis shows that four types of on-site pair potentials are allowed. Using the symmetries of the wallpaper group $p4g$ and the one-dimensional topological invariants, we clarify that, for the $A_{1u}$ representation, wallpaper fermions and two Majorana Kramers pairs coexist, and hybridization between them gives rise to a double-twisted surface state and produces four peaks in the surface density of states. We further find that the mirror Chern number vanishes, indicating that our system realizes mirror-helicity-free surface states. This distinguishes superconducting wallpaper fermions from the other superconducting topological (crystalline) insulators, such as ${\mathrm{Cu}}_x{\mathrm{Bi}}_2{\mathrm{Se}}_3$ and ${\mathrm{Sn}}_{1-x}{\mathrm{In}}_x\mathrm{Te}$.

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• Superconductivity
• Topological insulators
• Topological superconductors
• Green's function methods
• Symmetries in condensed matter
• Tight-binding model