SDSS J162520.29+120308.7-a new SU Ursae Majoris star in the period gap

We report results of an extensive world-wide observing campaign devoted to the recently discovered dwarf nova SDSS J162520.29+120308.7 (SDSS J1625). The data were obtained during the July 2010 eruption of the star and in August and September 2010 when the object was in quiescence. During the July 2010 superoutburst, SDSS J1625 clearly displayed superhumps with a mean period of P-sh = 0.095942(17) days (138.16 +/- 0.02 min) and a maximum amplitude reaching almost 0.4 mag. The superhump period was not stable, decreasing very rapidly at a rate of. P = -1.63(14) x 10(-3) at the beginning of the superoutburst and increasing at a rate of. P = 2.81(20) x 10(-4) in the middle phase. At the end of the superoutburst, it stabilized around the value of P-sh = 0.09531(5) day