We report here new data on pressure dependence of Fe-Mg partitioning between (Mg, Fe)SiO3 perovskite (Pv) and magnesiowüstite (Mw), KPv/Mw and (Mg, Fe)SiO3 Postperovskite (PPv) and Mw, KPPv/Mw, up to 123.6 GPa at 1600 K measured by synchrotron X-ray diffraction method and analytical transmission electron microscopy (ATEM). We observed a high FeO content in PPv coexisting with Mw [KPPv/Mw = (FeO/MgO)PPv/(FeO/MgO)Mw = 0.30] compared to that in Pv [Kpv/Mw = (FeO/MgO)Pv/ (FeO/MgO)Mw = 0. 12] observed from 23.0 to 95.4 GPa. KPv/Mw keeps a constant value of 0.12 up to the PPv phase boundary. Our results also support the possibility that a metallic phase may form in the lower mantle. The assemblage of PPv and Mw is 1.5-1.7% denser than the Pv bearing assemblage, which results in a gravitational stabilization of the lowermost mantle.