The reaction of Au(OH)(3) and oleum (65% SO3) in the presence of M2SO4 (M = Li, Na) afforded yellow single crystals of Li[Au(S2O7)(2)] (triclinic, P (1) over bar, Z = 1, a = 532.20(3), b = 649.69(4), c = 836.72(5) pm, alpha = 107.982(2), beta = 90.171(2), gamma = 102.583(2)degrees, V = 267,80(3) angstrom(3)) and Na[Au(S2O7)(2)] (monoclinic, P2(1)/n, Z = 2, a = 533.31(3), b = 1193.38(7), c = 907.67(5) pm, beta = 98.548(3)degrees, V = 571.26(6) angstrom(3)). Both compounds exhibit the unprecedented [Au(S2O7)(2)](-) anion in which a square planar coordination of the central gold atom is achieved by the chelating attachment of two disulfate groups. The disulfates were characterized by means of IR spectroscopy and DTA/TG measurements. For both compounds, the decomposition occurs via several steps and is finished at about 450 degrees C at the stage of elemental gold and the sulfates M2SO4 (M = Li, Na), as revealed by X-ray powder diffraction of the residues.