The unknown peaks in the SPXRD pattern with the composition of Ba16Y50Ru4Si29O157 were indexed to a tetragonal unit cell (a = 18.92732(1), c = 5.357307(6) Å) using TOPAS Academic V7. The reflections were consistent with a body-centred unit cell with mmm Laue class. The experimental pattern was described using Le Bail profile fit, and these data was processed by a charge flipping algorithm within the SuperFlip 40 tool of the Jana2020 package to obtain a preliminary structural model. The two best initial solutions corresponded to models with I4/mmm and I4 � 2m space group symmetry, however, both of the models contained additional oxygen and silicon sites with unreasonable interatomic distances and poorly fitted the experimental data. Therefore, the particles of this sample were analysed by means of CRED (selected sections of reciprocal space and systematic absences analysis are given in SI3), which by means of direct methods yielded a much cleaner model with clearly recognisable atomic environments (Figure ) consistent with I4 � 2m space group (Figure , a). No signs of possible superstructure reflections have been observed. Some atomic sites had to be populated with different species to satisfy geometric and coordination restrictions, but the final model corresponded to a charge-balanced formula Ba10Y26Si16O81, which is in good agreement with the composition revealed by EDX (average of Ba 10.72 ± 0.98 : Y 23.82 ± 1.95 : Si 16 ± 1.65, Figure ). The refinement of CRED data has converged with a final Rint of 21.78% (Table ) which is in line with recent literature values . The content of Ru from EDX analysis was lower than the detection limit, and further synthetic experiments proved that no Ru is incorporated in the structure of Phase A. ).