Histone H3-like variant which exclusively replaces conventional H3 in the nucleosome core of centromeric chromatin at the inner plate of the kinetochore (PubMed:11483958, PubMed:16839185). Required for recruitment and assembly of kinetochore proteins, mitotic progression and chromosome segregation (PubMed:24703848, PubMed:11483958, PubMed:16839185). May serve as an epigenetic mark that propagates centromere identity through replication and cell division (PubMed:11483958, PubMed:16839185). Forms a nucleosome-like histone octamer containing two molecules each of H2A, H2B, cid and H4 assembled in one cid-H4 heterotetramer and two H2A-H2B heterodimers (By similarity). The cid-H4 heterotetramer is more compact and structurally more rigid than corresponding H3-H4 heterotetramers (By similarity). Interacts with the condensin subunit Cap-G (PubMed:15592865). Interacts with Chrac-14 (PubMed:24703848). Localizes exclusively in the kinetochore domain of centromeres. Co-expressed with yemalpha. Belongs to the histone H3 family.