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We present experimental observations of interference between an atomic spin coherence and an optical field in a Λ-type gradient echo memory. The interference is mediated by a strong classical field that couples a weak probe field to the atomic coherence through a resonant Raman transition. Interference can be observed between a prepared spin coherence and another propagating optical field, or between multiple Λ transitions driving a single-spin coherence. Our scheme can behave as a controllable time-delayed beamsplitter with dynamically tuneable splitting ratio and allows, in principle, for unity interference visibility.