Is it proper to use an ampersand in french?

Yes, it is proper to use an ampersand in French. It is used to join two words or names together, such as Louis & Louise, or as an abbreviation for the word et, which means "and". For example:

- Jean & Marie sont en voyage. (Jean and Marie are on a trip.)

- Le chien & le chat sont amis. (The dog and the cat are friends.)

- L'entreprise est ouverte du lundi au vendredi de 9h à 18h. (The business is open from Monday to Friday from 9am to 6pm.)