All the Disorder Mechanisms in the 13:58 Phases Come Together. Out of the Modulated Confusion Rises the Remarkable Phase Ce12.60Cd58.68(2)

The compound $Ce_{12.60}Cd_{58.68(2)}$ is a metrically commensurate representative of the incommensurately modulated phase $Ce_{13}Cd_{57+\delta}$. It is most likely a lock-in phase. The structure, which was solved using seeding of the modulation from those positions most affected as well as direct solution by charge flipping, represents a rare case of ordering in a family of structures where disorder is the rule. The disorder mechanisms, known from other $RE_{13}Zn/Cd_{58}$ phases, order in this phase to give rise to a remarkable interplay between interstitials and vacancies. The compound crystallizes in the super space group $Ccmm(\alpha 00)00s$ (standard setting $Amma(00\gamma )s00$) with cell parameters a = 27.2789(14) A, b = 15.7592(1) A, and c = 15.5816(4) A and a q vector close to 2/3.