A search is performed for a heavy particle decaying into different-flavor, dilepton pairs (eμ, eτ or μτ), using 36.1 fb−1 of proton-proton collision data at s=13 TeV collected in 2015–2016 by the ATLAS detector at the Large Hadron Collider. No excesses over the Standard Model predictions are observed. Bayesian lower limits at the 95% credibility level are placed on the mass of a Z′ boson, the mass of a supersymmetric τ-sneutrino, and on the threshold mass for quantum black-hole production. For the Z′ and sneutrino models, upper cross-section limits are converted to upper limits on couplings, which are compared with similar limits from low-energy experiments and which are more stringent for the eτ and μτ modes.1 MoreReceived 18 July 2018DOI:https://doi.org/10.1103/PhysRevD.98.092008Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI. Funded by SCOAP3.© 2018 CERN, for the ATLAS CollaborationPhysics Subject Headings (PhySH)PropertiesFlavor symmetriesParticles & Fields