We present the first results from an XMM-Newton serendipitous medium-deep survey , which covers nearly three square degrees .
We detect a total of 1022 , 495 and 100 sources , down to minimum fluxes of about 5.9 \times 10 ^ { -16 } , 2.8 \times 10 ^ { -15 } and 6.2 \times 10 ^ { -15 } erg cm ^ { -2 } s ^ { -1 } , in the 0.5-2 , 2-10 and 4.5-10 keV band , respectively .
In the soft band this is one of the largest samples available to date and surely the largest in the 2-10 keV band at our limiting X-ray flux .
The measured Log ( N ) -Log ( S ) are found to be in good agreement with previous determinations .
In the 0.5-2 keV band we detect a break at fluxes around 5 \times 10 ^ { -15 } erg cm ^ { -2 } s ^ { -1 } .
In the harder bands , we fill in the gap at intermediate fluxes between deeper Chandra and XMM-Newton observations and shallower BeppoSAX and ASCA surveys .