The compounds K2Zr(SO4)(3)<middle dot>2.5H(2)O, K2Zr(SeO4)(3), and K2Zr2O(SeO4)(4) were synthesized at 200 degrees C by reaction of Zr2O2(CO3 )(OH)(2) and KHCO(3 )with the respective acids H2SeO4/H2SO4 and minor H2O. Zr(OH)(2)(SeO4)<middle dot>H2O originates from an analo-gous experiment at 215 degrees C without KHCO3 . All four phases form colorless crystals up to several tenths of a mm and were investigated by single crystal X-ray diffraction. K2Zr(SO4)(3 )<middle dot>2.5H(2)O is monoclinic, space group P21/c (No. 14), with a = 7.295(2) & Aring;, b = 13.925(3) & Aring;, c = 12.579(3) & Aring;, beta = 95.32(3)degrees, V = 1272.3(4) & Aring;3, Z = 4, R1 = 0.025. K2Zr(SeO4)(3 ) and K2Zr2O(SeO4)(4) are both triclinic, space group P1 (No. 2), with a = 7.570(1) & Aring;, b = 10.500(1) & Aring;, c = 14.400(1) & Aring;, alpha = 85.55(1)degrees, beta = 88.04(1)degrees, gamma = 87.82(1)degrees, V = 1139.7(2) & Aring;3, Z = 4, R1 = 0.049, and a = 5.400(1) & Aring;, b = 7.328(1) & Aring;, c = 9.642(1) & Aring;, alpha = 95.81(1)degrees, beta = 95.20(1)degrees, gamma = 94.27(1)degrees, V = 376.74(4) & Aring;(3), Z = 1, R1 = 0.020, respectively. Zr(OH)(2)(SeO4)<middle dot>H2O crystal-lizes in the monoclinic space group C2/c (No. 15), with a = 6.684(1) & Aring;, b = 12.998(2) & Aring;, c = 6.792(1) & Aring;, beta = 97.37(1)degrees, V = 585.14(6) & Aring;(3), Z = 2, R1 = 0.013. [GRAPHICS]