After the discovery of a Higgs boson at the LHC in 2012 the question whether the observed particle is the Higgs boson as predicted by the Standard Model (SM) or it is part of an extended scalar sector still remains open. One possible extension of the Brout-Englert-Higgs mechanism are Two-Higgs-Doublet models where a second, complex doublet is postulated leading to five expected Higgs bosons in total. One of them is a heavy, pseudo-scalar Higgs boson A; the observed SM-like Higgs boson with a mass of ~125 GeV is identified with the light CP-even Higgs boson h. I will present a search for the Higgs boson A via its decay into a Z boson and a SM-like Higgs boson h with the ATLAS experiment at the LHC in proton-proton collisions with a center-of-mass energy of 13 TeV. The analysis exploits events where the Z boson decays into leptons and the Higgs boson into a pair of b quarks. In order to cover a mass range from 200 GeV up to 2 TeV also dedicated techniques to reconstruct boosted b-quark pairs are used. Previous and recent analyses are discussed with the focus on the one of the full dataset of the years 2015 and 2016.
