model, the AM texture of the lower $d_{xz/yz}$ band is completely missing and that of the upper $d_{xz/yz}$ is not quantitatively correct.

[**Band splitting near the $\mathrm{X}$ point.**]{} As shown in Table \[tab:heff\], the lowered symmetry $C_{2v}$ at $\mathrm{X}$ allows the mixture of Rashba and linear Dresselhaus terms in general (see Appendix A), with the linear Dresselhaus larger in magnitude, as shown in Fig. \[fig:am\]d. Due to the anisotropic dispersion of $d_{xz/yz}$ bands, the lowest conduction band at $\mathrm{X}=(\pi,0)$ mainly consists of $d_{yz}$ state. We find that the larger band splitting along $\mathrm{X}$—$\mathrm{M}$ comes from the $t_{2g}$-$e_g$ coupling whereas the smaller splitting along $\mathrm{X}$—$\Gamma$ is due to the intra-$t_{2g}$ coupling. Hence, the giant Rashba-Dresselhaus splitting in vicinity of $\mathrm{X}$ ($\approx 180$ meV) is due to the $e_g$ contribution. It has been recently pointed out [-@Chung2015] that this Rashba-Dresselhaus splitting along $\mathrm{X}$—$\mathrm{M}$ is necessary for weak topological superconductivity, which gives rise to dislocation Majorana zero modes. The Rashba-Dresselhaus splitting near $\mathrm{X}$ also affects the superconducting instability, as it splits the logarithmic van Hove singularity (VHS) of the $d_{xz/yz}$ band saddle point and shifts them away from $\mathrm{X}$ (see Appendix B for the logarithmic VHS splitting). Given that the splitting results in 