I once know a band of hippies in the Ardèche who, objecting to a rally being held locally, applied a "tack coat" to some of the roads. Only they were of the pointed steel variety.

PIARC/AIPCR gives this as couche d'accrochage. Meanwhile, back at the ranch, Dico-TP also gives couche d'accrochage - Couche de liant dont le but est d'assurer la liaison entre deux couches de chaussée - and gives enduit d'accrochage as a synonym.

I think there may have been collusion since the BSI Gloss of Bldg and Civ Eng Terms gives:
tack coat Thin film of binder to improve the adhesion between two courses.

Wot, between main and dessert?