Reported are the syntheses, crystal structure determinations from single-crystal X-ray diffraction, and magnetic properties of two new ternary compounds, Eu 11 Cd 6 Sb 12 and Eu 11 Zn 6 Sb 12 . Both crystallize with the complex Sr 11 Cd 6 Sb 12 structure type-monoclinic, space group C2/m (no. 12), Z ¼ 2, with unit cell parameters a ¼ 31.979(4) A ˚, b ¼ 4.5981(5) A ˚, c ¼ 12.3499(14) A ˚, b ¼ 109.675(1)1 for Eu 11 Zn 6 Sb 12 , and 1)1 for Eu 11 Cd 6 Sb 12 . Their crystal structures are best described as made up of polyanionic 1 1 ½Zn 6 Sb 12 22À and 1 1 ½Cd 6 Sb 12 22À ribbons of corner-shared ZnSb 4 and CdSb 4 tetrahedra and Eu 2+ cations. A notable characteristic of these structures is the presence of Sb-Sb interactions, which exist between two tetrahedra from adjacent layers, giving rise to unique channels. Detailed structure analyses shows that similar bonding arrangements are seen in much simpler structure types, such as Ca 3 AlAs 3 and Ca 5 Ga 2 As 6 and the structure can be rationalized as their intergrowth. Temperature-dependent magnetization measurements indicate that Eu 11 Cd 6 Sb 12 orders anti-ferromagnetically below 7.5 K, while Eu 11 Zn 6 Sb 12 does not order down to 5 K. Resistivity measurements confirm that Eu 11 Cd 6 Sb 12 is poorly metallic, as expected for a Zintl phase.