All the Disorder Mechanisms in the 13:58 Phases Come Together. Out of the Modulated Confusion Rises the Remarkable Phase Ce_12.60Cd_58.68(2)

The compound Ce12.60Cd58.68(2) is a metrically commensurate representative of the incommensurately modulated phase Ce13Cd57+δ. 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 RE13Zn/Cd58 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(α00)00s (standard setting Amma(00γ)s00) with cell parameters a = 27.2789(14) Å, b = 15.7592(1) Å, and c = 15.5816(4) Å and a q vector close to 2/3.