Nonreciprocal charge transport, characterized by direction-dependent electrical response, provides a powerful probe of electronic structure and a platform for rectification. However, its realization is typically governed by intrinsic crystal symmetry, restricting the range of suitable materials. Here, we demonstrate nonreciprocal charge transport in an otherwise centrosymmetric superconductor, ${\mathrm{FeTe}}_{0.7}{\mathrm{Se}}_{0.3}$, through kink-boundary-induced strain engineering. The stress relaxation during growth generates a cusplike kink-band boundary with asymmetric curvature, producing a spatially nonuniform strain field and an effective in-plane polarity that breaks inversion symmetry. Pronounced nonreciprocal transport is observed under out-of-plane magnetic fields, with strong dependence on current and temperature across the superconducting transition, in contrast to the negligible response in flat nanosheets. Our results identify kink-boundary-induced symmetry breaking as a general route to engineer nonreciprocal charge transport in centrosymmetric systems.

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• Grain boundaries
• Superconductivity