The amine-templated uranyl selenate (H₃O)₂[C ₁₂H₃₀N₂]₃-[(UO₂) ₄(SeO₄)₈](H₂O)₅ (1) has been prepared. Its structure [monoclinic, P2₁/n, a = 11.3437(7), b = 24.8042(12), c = 29.2496(19) Å, β= 96.701(5)°, V = 8173.8(8) ų, Z = 4, R₁ = 0.083] is based upon strongly undulating [(UO₂)(SeO₄)₂]^2- sheets consisting of corner-sharing UO₇ bipyramids and SeO₄ ^2- tetrahedra. The undulations of the adjacent sheets have an anti-phase character that allows the formation of large eliptical channels that are occupied by rod micelles formed by self-assembly of protonated 1,12-dodecanediamine molecules.