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Ultra-hot Jupiters are highly irradiated gas giants with equilibriumtemperatures typically higher than 2000K. Atmospheric studies of these planetshave shown that their transmission spectra are rich in metal lines, with someof these metals being ionised due to the extreme temperatures. Here, we use twotransit observations of WASP-76b obtained with the CARMENES spectrograph tostudy the atmosphere of this planet using high-resolution transmissionspectroscopy. Taking advantage of the two channels and the coverage of the redand near-infrared wavelength ranges by CARMENES, we focus our analysis on thestudy of the CaII infrared triplet (IRT) at 8500A and the HeI triplet at10830A. We present the discovery of the CaII IRT at 7$\sigma$ in the atmosphereof WASP-76b using the cross-correlation technique, which is consistent withprevious detections of the CaII H&K lines in the same planet, and with theatmospheric studies of other ultra-hot Jupiters reported to date. The low massdensity of the planet, and our calculations of the XUV irradiation received bythe exoplanet, show that this planet is a potential candidate to have a HeIevaporating envelope and, therefore, we performed further investigationsfocussed on this aspect. The transmission spectrum around the HeI triplet showsa broad and red-shifted absorption signal in both transit observations.However, due to the strong telluric contamination around the HeI lines and therelatively low signal-to-noise ratio of the observations, we are not able tounambiguously conclude if the absorption is due to the presence of helium inthe atmosphere of WASP-76b, and we consider the result to be only an upperlimit. Finally, we revisit the transmission spectrum around other lines such asNaI, LiI, H$\alpha$, and KI. The upper limits reported here for these lines areconsistent with previous studies.

CARMENES detection of the CaII infrared triplet and possible evidence of HeI in the atmosphere of WASP-76b