Differential and double-differential distributions of kinematic variables of leptons from decays of top-quark pairs ( toverline{t} ) are measured using the full LHC Run 2 data sample collected with the ATLAS detector. The data were collected at a pp collision energy of sqrt{s} = 13 TeV and correspond to an integrated luminosity of 140 fb−1. The measurements use events containing an oppositely charged eμ pair and b-tagged jets. The results are compared with predictions from several Monte Carlo generators. While no prediction is found to be consistent with all distributions, a better agreement with measurements of the lepton pT distributions is obtained by reweighting the toverline{t} sample so as to reproduce the top-quark pT distribution from an NNLO calculation. The inclusive top-quark pair production cross-section is measured as well, both in a fiducial region and in the full phase-space. The total inclusive cross-section is found to beσtt¯=829±1stat±13syst±8lumi±2beampb,\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ {\\sigma}_{t\\overline{t}}=829\\pm 1\\ \\left(\ extrm{stat}\\right)\\pm 13\\ \\left(\ extrm{syst}\\right)\\pm 8\\ \\left(\ extrm{lumi}\\right)\\pm 2\\ \\left(\ extrm{beam}\\right)\\ \ extrm{pb}, $$\\end{document}where the uncertainties are due to statistics, systematic effects, the integrated luminosity and the beam energy. This is in excellent agreement with the theoretical expectation.