APPENDIX FIGURE 1. Correlation of observed reflections in reciprocal space. We show the array of a total of 10 reflections in two different parallel projections. The reflections establish two intersecting sequences of reciprocal lattice vectors thus spanning a two-dimensional reciprocal lattice. The observable portion of reciprocal space is essentially two-dimensional since the sample containing Mao-Bell type diamond anvil cell could not be rotated during the experiment. The two-dimensional character of the available set of reflections does not permit rigorous indexing. We, therefore, considered the 2 angles of the observed reflections only and compared them to predicted values of perovskite, CaIrO3-type post-perovskite and kinked post-perovskites as shown in Table 1.