  In intermediate-temperature (T = 2.5 - 4.5 keV) galaxy clusters, abundance
measurements are almost-equally driven by Fe K and L transitions, at $\sim$ 6.7
keV and 0.9 - 1.3 keV, respectively. While K-shell-derived measurements are
considered reliable, the resolution of the currently available instrumentation,
as well as our current knowledge of the atomic processes, makes the modelling
of the L-line complex challenging, resulting in potential biases for abundance
measurements. In this work, we study systematics related to the modelling of
the Fe L-line complex that may influence iron-abundance measurements in the
intermediate-temperature range. To this aim, we select a sample of three bright
galaxy clusters, with long XMM-Newton observations available and temperature in
the 2.5 - 4.5 keV range. We fit spectra extracted from concentric rings with
APEC and APEC+APEC models, by alternatively excluding the L and K bands, and
derive the fractional difference of the metal abundances, $\Delta Z/Z$, as
indication of the consistency between K- and L-shell-derived measurements. The
$\Delta Z/Z$ distribution is then studied as a function of the cluster radius,
ring temperature and X-ray flux. The L-induced systematics, measured through an
individual fit of each MOS and pn spectrum, remain constant at a 5 - 6% value
in the whole 2.5 - 4.5 keV temperature range. Conversely, a joint fit of MOS
and pn spectra leads to a slight excess of 1 - 2% in the above estimate. No
significant dependence on the ring X-ray flux is highlighted. The measured 5 -
8% value indicates a modest contribution of the systematics to the derived iron
abundances, giving confidence for future measurements. To date, these findings
represent the best-achievable estimate of the systematics in analysis, while
future microcalorimeters will significantly improve our understanding of the
atomic processes underlying the Fe L emissions.
