Ordering driven superconductivity in an alkaline iron selenide*

Combining the resistivity, synchrotron x-ray diffraction, and neutron diffraction measurements, we investigated the evolution of the structural, magnetic, and superconducting properties with pressure up to 37 GPa of superconducting Rb$_{0.347}$Tl$_{0.347}$Fe$_{1.752}$Se$_{2}$. Extended phase diagram of temperatures and pressure were established for this material. The results show the superconductivity is in reality driven by ordering.