Here we propose an antipodal conjecture, which is based on the synthetic scheme of alkalide [K(C222)]⁺K^- , to prepare K⁺[K(CO)₈]^-. By introducing the concept of antipodal salts of alkalides, K⁺[K(CO)₈]^- is defined as antipodal salt of [K(C222)]⁺K^-. As Group 1 elements of the Periodic Table, the alkali metal K is conventionally considered to form chemical bonding through its 4s and 4p valence orbitals. Our theoretical results show that the 3d orbitals of K element in >[K(CO)₈]^- participate in chemical bonding of >[K(CO)₈]^-. This makes the alkali metal K shows typical transition metal chemical properties, which also provides the possibility for the synthesis of K⁺[K(CO)₈]^-. Based on the Born-Haber thermodynamic cycle, the upper-limit stable temperature of K⁺[K(CO)₈]^- is estimated to be 24.426 K . Our theoretical results indicate that antipodal salts of alkalides will be a new family of compounds with good synthetic prospects.