In the phase diagram of an excellent extractant of rare earth metal ions, di(2-ethylhexyl) phosphate (HDEHP,commercial name P204), mixing with a cationic trimethyltetradecylammonium hydroxide (TTAOH) in water,a birefringent L
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phase was found, which consists of densely stacked multilamellar vesicles. The denselystacked multilamellar vesicles are remarkably deformed, as observed by means of cryotransmission electronmicroscopy (cryo-TEM). Further, self-assembled structures-oligovesicular vesicles, bilayer cylinders, andtubes joining with vesicles-were also observed. The self-assembled phase is transparent, anisotropic, andhighly viscous, possessing elastic properties determined by rheological measurements. This is the first timethat birefringent L
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phase with remarkably deformed amphiphilic bilayer membranes has been constructedthrough combining a hydrophobic organic extractant having double chains with a water-soluble surfactanthaving a single chain, which may direct primarily toward acquiring an understanding of the mechanism ofsalt-free catanionic vesicles and secondarily to determine if vesicle-extraction technology utilizing extractantsis possible.