[en] K_0.75MoNbP₃O₁₂, M_r=503.009, orthorhombic, Pbcm, a=8.8518 (5), b=9.1453 (11), c=12.5174 (11) A, V=1013.3 (3) A³, Z=4, D_x=3.300 Mg m^-3, λ(Mo Kα)=0.71073 A, μ=3.13 mm^-1, F(000)=953, T=294 K, R=0.029, wR=0.033 for 1235 observed reflections. This compound is isostructural with KMo₂P₃O₁₂-type oxides. Its framework is built up from MoO₆ octahedra and PO₄ tetrahedra which delimit tunnels running along b. Different from KMo₂P₃O₁₂, the tunnels are partly occupied by the potassium ions which are distributed at random. (orig.)