  The SIDDHARTA-2 experiment installed at the DA$\mathrm{\Phi}$NE collider of
INFN-LNF performed, for the first time, measurements of high-n transitions in
intermediate mass kaonic atoms during the data taking campaigns of 2021 and
2022. Kaonic carbon, oxygen, nitrogen and aluminium transitions, which occur in
the setup materials, were measured by using the kaons stopped in the gaseous
helium target cell with aluminium frames and Kapton walls, and are reported in
this paper. These new kaonic atoms measurements add valuable input to the
kaonic atoms transitions data base, which is used as a reference for theories
and models of the low-energy strong interaction between antikaon and nuclei.
Moreover, these results pave the way for future dedicated kaonic atoms
measurements through the whole periodic table and to a new era for the
antikaon-nuclei studies at low energy.
