For the first time dark brown single crystals of mixed-valent AgF[AgF4] were isolated under solvothermal conditions out of anhydrous HF/F-2. The compound crystallizes in a new type of structure, triclinic with a = 499.9(2) pm, b = 1108.7(5) pm, c = 735.7(3) pm, alpha = 90.05(3)degrees, beta = 106.54(4)degrees, gamma = 90.18(4)degrees, spcgr. P (1) over bar -C-i(1) (No. 2) and Z = 4.