We began the exploration of the BaO-Y2O3-SiO2-RuO2 chemical space with the BaRuO3-Y2Ru2O7-Y2Si2O7 phase field (highlighted in green in Figure ). The detailed description of the experimental methods used is given in SI1 while the main steps will be outlined below. The space was sampled initially through four evenly spaced compositions (see Figure ), and different synthetic temperatures (1273-1573 K) were used to maximize exploration efficiency. Most of the samples contained mixtures of known phases, however two of the powder samples that were heated to 1573 K presented diffraction patterns which could not be assigned to any of the known structures. The unknown peaks were identified, and further investigation has led to isolation of two phases: Ba5Y13[SiO4]8O8.5 (A) and Ba3Y2[Si2O7]2 (B).