with distribution mean m, step size σ and covariance matrix C. The population size and initial mean, m (0) , and step size, σ (0) , are user-defined. We refer to the initial mean as the founder structure. Starting from founders that were variations of published structures, we iteratively added data using the committee uncertainty estimate aggregated structure-wise 35 While two of the 35 initial CMA-ES searches produced the new stable configuration, a majority of these evolutionary searches were found to be prone to instability, specifically to the expulsion of an Sr atom. Although problematic structures could be identified manually, an active learning procedure needs to be able to identify and incorporate such structures into the training data based on computed quantities such as model uncertainties. Since this behaviour was not reflected in the aggregated structure uncertainty as defined in Eq. ( ), we utilized spatially resolved atomic uncertainties. These are obtained by aggregating over neighboring atoms within a cutoff radius (in the following set to 4 Å) instead of over the entire structure