  Vector-like quarks (VLQ) that couple preferentially to third-generation
Standard Model (SM) quarks are a well-motivated extension of the SM, which
could solve in particular the hierarchy problem. While VLQs can be produced in
pairs via the strong interaction at the LHC, the cross section for single
production may be larger than the pair production cross section for VLQ masses
above the current exclusion limits. An overview of the searches for the single
production of VLQs at the ATLAS experiment that use data taken at a
centre-of-mass energy of 13 TeV, corresponding to up to 79.8 fb$^{-1}$, is
presented. Vector-like top quarks are searched for in the decay channel
$T\rightarrow Wb$ and in the decay channel $T\rightarrow Zt$ with the $Z$ boson
decaying to two charged leptons. Vector-like bottom quarks are searched for in
the decay channel $B\rightarrow Hb$ with the Higgs boson decaying to two
photons. No significant excess over the SM prediction is found and 95% CL
exclusion limits are set on the single production of VLQs as a function of
their mass and coupling to SM quarks.
