This data set consists of time series of magnetotelluric data (electric and magnetic fields) at 16 sites recorded in the framework of the coordinated project IBERGIC-CAS. These data were collected in three fieldwork campaigns performed between June and November of 2023. The recorded time for each site ranged between 12 and 20 days. The raw data are as they come out of the instrument, without any additional processing, and only checked for coherence and editing to identify any missing data. They are presented as plain ASCII files containing the five components of the electromagnetic field at the surface measured by the instruments. Additionally, 16 image files (PNG format) are available to quickly visualise the time series of each site.