  One of the primary objectives of the TOPoS survey is to search for the most
metal-poor stars. Our search has led to the discovery of one of the most
iron-poor objects known, SDSS\,J092912.32+023817.0. This object is a multiple
system, in which two components are clearly detected in the spectrum. We have
analysed 16 high-resolution spectra obtained using the UVES spectrograph at the
ESO 8.2m VLT telescope to measure radial velocities and determine the chemical
composition of the system. Cross correlation of the spectra with a synthetic
template yields a double-peaked cross-correlation function (CCF) for eight
spectra, and in one case there is evidence for the presence of a third peak.
Chemical analysis of the spectrum obtained by averaging all the spectra for
which the CCF showed a single peak found that the iron abundance is
[Fe/H]=-4.97. The system is also carbon enhanced with [C/Fe]=+3.91 (A(C)=7.44).
From the permitted oxygen triplet we determined an upper limit for oxygen of
[O/Fe]<+3.52 such that C/O>1.3. We are also able to provide more stringent
upper limits on the Sr and Ba abundances ([Sr/Fe]<+0.70, and [Ba/Fe]<+1.46,
respectively).
