Results on $Lambda$p femtoscopy are reported at the lowest energy so far. At a beam energy of 1.76A~GeV, the reaction Ar+KCl was studied with the High Acceptance Di-Electron Spectrometer (HADES) at SIS18/GSI. A high-statistics and high-purity $Lambda$ sample was collected, allowing for the investigation of $Lambda$ p correlations at small relative momenta. The experimental correlation function is compared to corresponding model calculations allowing the determination of the space-time extent of the $Lambda$p emission source. The $Lambda$p source radius is found slightly smaller than the pp correlation radius for a similar collis ion system. The present $Lambda$p radius is significantly smaller than that found for Au+Au/Pb+Pb collisio ns in the AGS, SPS and RHIC energy domains, but larger than that observed for electroproduction from He. Taking into account all available data, we find the $Lambda$p source radius to increase almost linearly with the number of participants to the power of one-third.
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