Er3TlC is (Cubic) Perovskite structured and crystallizes in the cubic Pm-3m space group. The structure is three-dimensional and consists of one methane molecule and one Er3Tl framework. In the Er3Tl framework, Er is bonded in a linear geometry to two equivalent Tl atoms. Both Er–Tl bond lengths are 2.78 Å. Tl is bonded to six equivalent Er atoms to form corner-sharing TlEr6 octahedra. The corner-sharing octahedral tilt angles are 0°.