in Fig. \[fig:figsi1\], where we see that the spectral weight for the [$d_{xy}$]{} orbital dominated shallow electron band diminishes at higher temperatures, and recovers when cooled back down. This shows that the observed temperature-induced crossover is not due to any surface effects and is a robust bulk phenomenon.

![\[fig:figsi1\]Temperature cycle test on [K$_{x}$Fe$_{2-y}$Se$_2$]{} (a) Spectral images across X point measured at selected temperatures in the temperature cycle from 10K to 300K to 40K. Polarization geometry and photon energy is the same as that in Fig. \[fig:fig2\](a). (b) EDC at X point taken in the temperature cycle, where the peak around -0.05eV is the [$d_{xy}$]{}band bottom, whose spectral weight diminishes up to 300K and recovers when cooled back down.](FigSI1){width="45.00000%"}

Results on [Rb$_{x}$Fe$_{2-y}$Se$_2$]{}
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![image](FigSI2){width="90.00000%"}

We have done similar measurements on superconducting RFS as discussed in the main text for superconducting KFS. Fig. \[fig:figsi2\] summarizes the main results. RFS has similar electronic structure as KFS, including Fermi surface, band dispersions and their orbital characters, specifically there is a shallow electron band at X that is [$d_{xy}$]{} and a deep electron band that is [$d_{xz}$/$d_{yz}$]{}. Fig. S2d-f shows the temperature dependence of the electron bands, equivalent to Fig. \[fig:fig2\](a) for the KFS. Here 