In this paper the synthesis, conductivity, and structure of the garnet-related Li ion conductor, Li5Nd3Sb2O12, are reported. As for the related Li5La3M2O12 (M = Nb, Ta) materials, this phase shows high Li ion conductivity, with a conductivity at 300 degrees C of 9.2 x 10(-3) S cm(-1). Structural studies using neutron diffraction indicate a cubic unit cell, space group Ia-3d, with Li located in two partially occupied sites. One of the sites is the traditional garnet structure tetrahedral site, while the other Li site is considerably more distorted. Although the latter is nominally a six coordinate site, a close inspection suggests that the coordination could be described as distorted tetrahedral, with the remaining two bonds being significantly longer (approximate to 2.6 angstrom). (c) 2007 Elsevier Ltd. All rights reserved.