Herein we report the syntheses and the X-ray structure of [Cs8X27](19-) (X = Cl, Br) clusters, the first binary cluster anions isolated in bulk crystal structures. They were obtained by electrostatic capture and face-directed recognition of the prenucleation [Cs-m Cl-n]((n-m)-) clusters from water solutions, using [M-4(OH)(8)(OH2)(16)](8+) (M = Zr-IV or Hf-IV) as the counter cations. These compounds have been thoroughly characterized with a variety of techniques including vibrational spectroscopy and superionic conductivity analysis. This work not only provides structural models for a better understanding of the nucleation of binary materials but also shows that magic number binary clusters adopting a cubic lattice structure do form, in agreement with the time-honored theoretical and spectroscopic predictions.