Signature of angle-dependent electron localization in a unidirectional supermodulated van der Waals actinide: UOTe

Superlattices are fertile grounds for realizing novel quantum phases, as highlighted by recent discoveries in artificially-twisted van der Waals (vdW) moiré superlattices. However, improving the uniformity and scalability of these artificial moiré superlattices remains challenging. In this context, identifying a spontaneously-formed vdW superlattice with macroscopic coherence is a promising solution. Here we report the discovery of a unidirectional incommensurate supermodulation in the vdW Kondo material UOTe. Our electron microscopy measurements reveal intricate domain patterns formed by two orthogonal directions of the supermodulation, indicative of a spontaneous symmetry-breaking origin, which is further substantiated by our density functional theory calculations. Moreover, we find that the supermodulation can persist coherently over a macroscopic scale, allowing us to measure its angle-dependent transport properties. We observe an anisotropic resistance upturn, suggesting an angle-dependent electron localization. Our work establishes UOTe as a promising platform for investigating superlattice-emergent quantum phenomena on a clean and macroscopic scale.