  The first measurements of the production of muons and electrons from
heavy-flavour hadron decays in Xe-Xe collisions at $\sqrt{s_{\rm NN}}$ = 5.44
TeV, using the ALICE detector at the LHC, are reported. The measurement of the
nuclear modification factor $R_{\rm AA}$ is performed as a function of
transverse momentum $p_{\rm T}$ in several centrality classes at forward
rapidity ($2.5 < y <4$) and midrapidity ($\vert y \vert < 0.8$) for muons and
electrons from heavy-flavour hadron decays, respectively. A suppression by a
factor up to about 2.5 compared to the binary-scaled pp reference is observed
in central collisions at both central and forward rapidities. The $R_{\rm AA}$
of muons from heavy-flavour hadron decays is compared to previous measurements
in Pb-Pb collisions at $\sqrt{s_{\rm NN}}$ = 5.02 TeV. When the nuclear
modification factors are compared in the centrality classes 0-10% for Xe-Xe
collisions and 10-20% for Pb-Pb collisions, which have similar charged-particle
multiplicity density, a similar suppression, with $R_{\rm AA} \sim 0.4$ in the
$p_{\rm T}$ interval $4 < p_{\rm T} < 8$ GeV/$c$, is observed. The comparison
of the measured $R_{\rm AA}$ values in the two collision systems brings new
insights on the properties of the quark-gluon plasma by investigating the
system-size and path-length dependence of medium-induced parton energy loss.
The results of muons and electrons from heavy-flavour hadron decays provide new
constraints to model calculations.
