K-Means is outperformed for each target language, confirming the superiority of spectral clustering established in prior work, e.g., (Scarton et al., 2014).
we find results with another clustering algorithm, hierarchical agglomerative clustering with Ward's linkage (Ward, 1963), on par with spectral clustering (1.4 points on average in favour of spectral, which is better on 4 out of 6 languages).