The　two　title　compounds　obtained　by　solid　state　reaction　at　high　temperature　were　characterized　as　isomorphism　by　single-crystal　X-ray　diffraction.　The　space　group　of　both　crystals　is　C2-nu-4-Pma2,　with　lattice　constants　a　=　7.955(1),　b　=　6.258　(1),　c　=　7.203(2)　angstrom　for　I,　and　a　=　7.914　(1),　b　=　6.237　(1),　c　=　7.236　(1)　angstrom　for　II,　Z　=　2.　The　structures　were　determined　by　normal　method　and　refined　to　the　final　R　=　0.074　and　0.083,　respectively.　The　results　show　that　the　structure　may　be　regarded　as　building　by　cluster　unit　with　formula　Ni2M2Te4　(M　=　Nb　or　Ta)　in　which　two　Ni　atoms　and　two　M　atoms　form　a　rhombus,　while　the　Te　atoms　are　distorted　tetrahedrally　coordinated　with　both　kinds　of　metal　atoms.　In　the　cluster　unit　there　exist　interactions　between　Ni　atoms　as　well　as　between　Ni　and　M　atoms.　In　addition,　all　the　cluster　units　are　linked　together　not　only　by　bridging　Te　atoms,　but　also　by　weaker　metal-metal　interactions,　so　as　to　form　two-dimensional　network.　Therefore,　the　structure　may　be　represented　by　the　formula　[Ni2M2(mu-4-Te)6/3　(mu-4-Te)4/2]infinity.　A　preliminary　measurement　of　electric　conductivity　shows　that　the　crystals　of　the　two　title　compounds　are　metallic　but　their　conductivities　are　anisotropic;　those　parallel　to　the　a-b　axes　are　about　10(3)OMEGA-1　.　cm-1,　whereas　those　along　the　c　axis　are　about　10-OMEGA-1　.　cm-1.