The volume per (four) formula unit of the title compound is 274.025 Å 3 , which is only slightly smaller than that of the EuCdPt (277.6 Å³), as expected from smaller atomic size of Mn as compared to that of Cd. Therefore, the Eu are most likely divalent in the title compound as well. As such, the Eu2Mn0.89Cd1.11Pt2 phase is only the second true quaternary system with the Pd2(Mn,Pd)Ge2 type, in contrast to several known ternary LaNiAl type representatives, and their pseudo-ternary derivatives like the solid solutions CeRu1-xNixAl and CeRu1-xPdxAl did not exhibit any Ru/Ni or Ru/Pd (partial) ordering. Mixed valent Ce 3+/4+ was observed in all Ce representatives as well as in the solid solutions CeRu1-xNixAl and CeRu1-xPdxAl. Interestingly, despite the scarcity of trivalent Eu in intermetallic structures, numerous cases of valence phase transition are known in Eu compound with Pt, and the one of the most recent is a report on the temperature-controlled Eu valence transition in Eu2Al6Pt15 phase, which is therefore highly responsive to external stimuli without noticeable structural alteration. Similarly, partial displacement of selected atoms in the title structure by larger isovalent elements might result in significant chemical pressure, which can trigger Eu valence fluctuation as well. Having these aspects of the crystal chemistry of ternary Eu intermetallic with Pt in mind, the rare quaternary Eu2Mn0.89Cd1.11Pt2 phase, which combines high magnetic moment on f-metal Eu and d-metal Mn, as well as strong spin-orbit coupling in Pt atom may provide a unique plateform for the discovery of exotic physical properties. These characteristics may find applications in the development of more efficient magnetic refrigerants, since the current paradigm is to focus on maximizing the structural (lattice) contribution to the total entropy change in moderate magnetic fields. Illustrative enough, some Mn-based intermetallic phases with the orthorhombic TiNiSi-type structure are known to undergo diffusion-less (martensitic-like) structural transition to the high-temperature hexagonal Ni2In-type phases in paramagnetic (PM) state. Some of these compounds for example, MnCoGe and MnNiSi also exhibit magnetic transitions to ferromagnetic order. These findings suggest that Mnbased compounds with TiNiSi related structures may be prone to structural transitions and, in the title phase, a coupling between Eu valence fluctuation and Mn-Mn bonding may be one driving force for allowing magnetic and structural transitions to be coupled.