AbstractEuMg6Sn3.67 has been synthesized by reacting the mixture of the corresponding pure elements at high temperature, and structurally characterized by single-crystal X-ray diffraction study. EuMg6Sn3.67 crystallizes in hexagonal space group P63/m (No. 176) with a = 11.7259(4), c = 4.5507(2) Å, V = 541.88(4) Å3, Z = 2, Mr = 734.60, Dc = 4.502 g/cm3, μ = 14.348 mm-1, F(000) = 638, the final R = 0.0128 and wR = 0.0378 for 464 observed reflections with I > 2σ(I). EuMg6Sn3.67 is closely related to the Ba2Mg12Ge7.33 structure type and features a three-dimensional [Mg6Sn3.67] framework with one-dimensional hexagonal tunnels along the c-axis occupied by the Eu atoms. Electronic structure calculation indicates that the title compound is metallic.