Typical length scales associated with superconductivity are in the range of nanometers. Accordingly, measurements of electrical resistance over much larger distances are supposed to be insensitive to details of spatial inhomogeneities of superconducting order. We observe that current paths adopt a highly nonuniform distribution at the onset of the superconducting transition which is manifested in the development of a finite transverse resistance. The anisotropic distribution of current density indicates the emergence of electronic inhomogeneities perceivable over macroscopic distances, characterized by a length scale which is unrelated to the structural properties of the superconducting films. Our experiments reveal the ubiquitous nature of this phenomenon in conventional superconductors.

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• Critical phenomena
• Electrical conductivity
• Electronic phase separation
• Superconducting phase transition