A new tunnel Schottky diode based on SiC and a mixed conductor of BaSnO3 as the gate has been investigated. I-V curves at different operating temperatures and two different gas atmospheres have been measured. The device shows sensitivity to oxygen, with maximum at 400degreesC. A model that describes the behaviour of the device is proposed, which takes into account the different types of conduction of the BaSnO3 due to the temperature.