  The iron-based compounds of the so-called 12442 family are very peculiar in
various respects. They originate from the intergrowth of 122 and 1111 building
blocks, display a large in-plane vs. out-of-plane anisotropy, possess double
layers of FeAs separated by insulating layers, and are generally very similar
to double-layer cuprates. Moreover, they are stoichiometric superconductors
because of an intrinsic hole doping. Establishing their superconducting
properties, and in particular the symmetry of the order parameter, is thus
particularly relevant in order to understand to what extent these compounds can
be considered as the iron-based counterpart of cuprates. In this work we review
the results of various techniques from the current literature and compare them
with ours, obtained in Rb-12442 by combining point-contact Andreev-reflection
spectroscopy and coplanar waveguide resonator measurements of the superfluid
density. It turns out that the compound possesses at least two gaps, one of
which is certainly nodal. The compatibility of this result with the
theoretically allowed gap structures, as well as with the other results in
literature, is discussed in detail.
