BaTi$_{2}$As$_{2}$O and CeCr$_{2}$Si$_{2}$C are both in space group $P4/mmm$ #123, and use the same Wyckoff positions. They differ in the c/a ratio. We follow the ICSD and put them into separate prototypes.
$\frac{1}{2}a \,\mathbf{\hat{x}}+\frac{1}{2}a \,\mathbf{\hat{y}}- c z_{4} \,\mathbf{\hat{z}}$
(2h)
As I
References
X. F. Wang, Y. J. Yan, J. J. Ying, Q. J. Li, M. Zhang, N. Xu, and X. H. Chen, Structure and physical properties for a new layered pnictide-oxide: BaTi$_{2}$As$_{2}$O, J. Phys.: Condens. Matter 22, 075702 (2010), doi:10.1088/0953-8984/22/7/075702.
Found in
Y.-L. Sun, H. Jiang, H.-F. Zhai, J.-K. Bao, W.-H. Jiao, Q. Tao, C.-Y. Shen, Y.-W. Z., Z.-A. Xu, and G.-H. Cao, Ba$_{2}$Ti$_{2}$Fe$_{2}$As$_{4}$O: A New Superconductor Containing Fe$_{2}$As$_{2}$ Layers and Ti$_{2}$O Sheets, J. Am. Chem. Soc. 134, 12893–12896 (2012), doi:10.1021/ja304315e.
First cited in
N. Anderson, M. J. Mehl, H. Eckert, S. Divilov, X. Campilongo, S. Curtarolo, The AFLOW Library of Crystallographic Prototypes: Part 5. Submitted to Computational Materials Science (2026).