We report the discovery of the new dipping X–ray source , XMMU J004308.6+411247 , in M31 , during a systematic search for periodicities in XMM– Newton archival observations .
During the 2002 January 6 observation , the dips recur with a 107 min period and the source count rate is consistent with zero at the dip minimum .
Dips with the same modulation and period are also observed during the XMM– Newton observations carried out on 2000 June 25 , 2001 June 29 and the Chandra observation of 2001 October 5 .
The dips of XMMU J004308.6+411247 show no evidence of energy dependence .
The average X–ray flux of XMMU J004308.6+411247 is nearly constant across different observations ( \sim 10 ^ { 37 } erg s ^ { -1 } for an assumed M31 distance of 780 kpc in the 0.3–10 keV band ) ; the spectrum is well fit by an absorbed power law with a photon index \sim 0.8 
or an absorbed Comptonization model .
The photo-electric absorption is consistent with the Galactic value in the source direction .
If XMMU J004308.6+411247 is located in M31 its properties are consistent with those of dipping low mass X–ray binaries in the Galaxy .
Present observations do not allow to distinguish between dips and eclipses .

The possibility that XMMU J004308.6+411247 is a foreground X–ray source can not be ruled out at present ; in this case the source might be a magnetic cataclysmic variable .