Maître d’enseignement et de recherche (MER) are relatively rare positions which were apparently introduced in universities in the French-speaking area of Switzerland in the 1990s.
MER are part of the corps intermédiaire (German: Mittelbau) along with PhD researchers and postdoctoral researchers. They are very similar to the Maître-assistante (MA) positions, also unique to French-speaking universities in Switzerland, as far as I know, with the only difference that MER are open-ended after evaluation, whereas MA positions are fixed-term (this makes MER the only positions in the corps intermédiaire that can be open-ended).
As other positions of the corps intermédiaire, MER are not part of the decision-making in universities, normally have no assistants, and may be excluded from some internal resources. They are attached to a chair, which limits independence in teaching and research, and typically teach more than professors. Despite the R in the name, apparently some MER effectively teach full time. Compared to professors, MER and MA have a lower salary and are often employed part-time. Unlike Lecturers in the British system, no promotion is foreseen for MER (at all). In this sense, the ‘official’ translation of MER (and MA) into ‘senior lecturer’ is inaccurate.
Image credit: CC-by Jeena Paradies