2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/17462We investigated carbon substitution effect on boron plane of superconducting MgB$_2$. MgB$_2$ and MgB$_{1.8}$C$_{0.2}$ samples are synthesized under high pressure furnace. MgB$_{1.8}$C$_{0.2}$ are characterized as AlB$_2$-type single phase with smaller B-B distance. During the superconducting transition, two distinct onset temperatures are observed in MgB$_{1.8}$C$_{0.2}$.2 figuresSuperconductivityMaterials Sciencetext