This is a tetragonal distortion of the $L1_{2}$ (Cu$_{3}$Au) structure. When $c = a$ the atoms are at the positions of a face-centered cubic lattice. If we replace the Ti-I atom by Cu, then the system reduces to the $L1_{0}$ (CuAu) structure. Interestingly, (Massalski, 1986) lists no stable or metastable structures with composition CuTi$_{3}$. (Byström, 1947) do find a phase of CdAu$_{3}$ which they say has this structure.
N. Karlsson, An X–ray study of the phases in the copper–titanium system, J. Inst. Met. 79, 391–405 (1951).
T. B. Massalski, H. Okamoto, P. R. Subramanian, and L. Kacprzak, eds., Binary Alloy Phase Diagrams (American Society for Metals, Materials Park, OH, 1990).
A. Byström and K. E. Almin, X-ray Investigation of Gold-Cadmium Alloys Rich in Gold, Acta Chem. Scand. 1, 76–89 (1947), doi:10.3891/acta.chem.scand.01-0076.
Found in
P. Villars and K. Cenzual, Pearson's Crystal Data – Crystal Structure Database for Inorganic Compounds (2013). ASM International.
First cited in
M. J. Mehl, D. Hicks, C. Toher, O. Levy, R. M. Hanson, G. L. W. Hart, and S. Curtarolo, The AFLOW Library of Crystallographic Prototypes: Part 1, Comp. Mat. Sci. 136, S1-S828 (2017). (doi=10.1016/j.commatsci.2017.01.017)