the CBM consist of $t_{2g}$ ($d_{xy}$, $d_{xz}$, $d_{yz}$) states of Ta in the outermost layer, with the calculated bandwidth of $\approx$ 1.7 eV for the $d_{xz/yz}$ bands. These bands being 2D, the triple degeneracy (excluding spin) of the $t_{2g}$ bands at $\Gamma$ is lifted, splitting the $d_{xy}$ and the $d_{xz/yz}$ manifolds; the Ta atomic SOC further splits the $d_{xz/yz}$ bands into upper and lower $d_{xz/yz}$ states. Finally, when the ISB at the surface is accounted for, the Rasha-type band splitting lifts spin degeneracies in the entire Brillouin zone (BZ) except at the time-reversal invariant momenta $\Gamma$, $\mathrm{X}$ and $\mathrm{M}$. We note that this Rashba-type band splitting of the $d_{xz/yz}$ bands is strikingly larger in magnitude than that of the $d_{xy}$ bands, contrary to the prediction of the $t_{2g}$-only model [-@Khalsa2013; -@YKim2013; -@Scheurer2015]. Moreover, our calculation gives the Rashba coefficient of the lower $d_{xz/yz}$ bands at $\Gamma$ of $\alpha_R \approx 0.3~\mathrm{eV\AA}$, which is an order of magnitude larger than that of LAO/STO heterostructure deduced from the experimental magnetoresistance data [-@Caviglia2010], and the Rashba energy of $E_R \gtrsim 15~\mathrm{meV}$; these values are also significantly larger than $\alpha_R \approx 0.1~\mathrm{eV\AA}$, $E_R \approx 1~\mathrm{meV}$ for the bilayer case of Fig. \[fig:atomicstr\]c. The Rashba-Dresselhaus effect 