Quantitative syntheses, structure determinations and interpretations, and band calculations are reported for the nonstoichiometric rhombohedral (R (3) over barc) and monoclinic (C2/c) Sr2Au6(Au3-xTx) (T = Zn, Go) compounds. Several different compositions of the two Sr phases were similarly refined from single crystal X-ray diffraction data as R (3) over barc: a approximate to 8.43 angstrom, c approximate to 21.85 angstrom, Z = 6 and C2/c: a approximate to 14.70 angstrom, b approximate to 8.47 angstrom, c approximate to 8.70 angstrom, beta approximate to 123.2 degrees, Z = 4. The R (3) over barc Zn phase is stable in the composition region x similar to 2.5-2.9 whereas its C2/c neighbor is the major product at x similar to 2.2-2.3. Gallium versions of both were also identified. Both R (3) over barc and C2/c structural types contain hexagonal-diamond-like gold superlattices stuffed with strings of interstitial Sr and disordered triangular (Au,T)(3) units. The latter space group is a maximal, nonisomorphic subgroup of the former, and the decrease in interstitial radius from Ba to Sr (similar to 0.08 angstrom experimentally) evidently drives the symmetry reduction, relaxation, and small distortions, principally around the Sr sites. Au-Au bonding among the Au hexagons in the host lattices and with gold components in the triangular interstitials is dominant and reflected in their tight packing and short interatomic separations.