The realization of a Weyl semimetal hosting a minimal single pair of Weyl points (WPs) is a long-standing goal for fundamental studies of chiral fermions, yet remains elusive in nonmagnetic electronic materials. Here, through first-principles calculations and symmetry analysis, we propose a stable, all-${\mathit{sp}}^2$ hybridized three-dimensional carbon allotrope, $\mathrm{HSRDC}\text{−}{\mathrm{C}}_{28}$. Crucially, its low-energy bands host exactly one pair of WPs at the time-reversal-invariant momenta $\mathrm{\Gamma }$ and M, carrying topological charge $C=\pm 2$, with the sign of the charge tied to the structural chirality. These WPs exhibit characteristic anisotropic dispersions, linear along the $C_4$-rotation axis and quadratic in the plane perpendicular to this axis, and are protected by $C_4$-rotation and time-reversal symmetries. The calculated surface states exhibit ultralong double-Fermi arcs connecting the projections of $\mathrm{\Gamma }$ and M, spanning the entire surface Brillouin zone and providing unambiguous signatures for experimental verification. Our work not only expands the landscape of topological quantum states but also offers a nonmagnetic electronic platform for exploring the physics associated with minimal double-Weyl fermions.

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• Symmetry protected topological states
• Carbon-based materials
• Weyl semimetal
• First-principles calculations