092000

We propose to observe 32 (28 with new exposures) among the brightest galaxygroups and clusters selected from the eFEDS sample with a total exposure time of226 ks.We will use the requested data to determine their temperatures to measure thespectral cross-calibration uncertainties between eROSITA and XMM-Newton.The size of the selected sample together with its temperature coverage willallow a firm constraint of any systematic difference between the two instrumentsand how this difference (if any) depends on the spectral temperature itself.Considering the current situation on the eROSITA} operations we notice thatthe eFEDS exposure will be unmatched in the next future providing a unique sample to investigate any cross-calibration among X-ray instruments. [truncated! Please see actual data for full text]