First spectroscopic observations with the 14-m radio telescope at theCentro Astronomico de Yebes : SiO masers in evolved stars.

We present observations of the SiO (v=l and 2, J=l-O) transitions at 43 GHz towards 40 objects, as a first step in an extensive observing program of SiO maser emission from evolved stars that we are carrying out at the Centro Astronomico de Yebes. The detection of 12 new SiO stars and the confirmation of one previous tentative detection are reported. A careful choice of objects with respect to infrared flux and stellar phase has yielded a high detection rate for oxygen-rich Mira variables, in spite of our moderate sensitivity. These are the first spectroscopic results obtained with the l4-m mm-wave radio telescope at Yebes, the system is briefly described in the text.