Lemar began playing football at a local club in Guadeloupe's capital Pointe- a-Pitre. In summer 2010, the then 14 -year-olds were indeed also offers the French top club AS Saint- Étienne and Olympique Marseille, but he decided in favor of SM Caen and joined the club on the French mainland. The youth players as technically strong force was first considered in December 2011 and thus shortly after his 16th birthday for the second team of his club; for the fourth division team, he ran regularly from now on, although he continued to play in parallel for the youth.
In March 2013 he signed a valid from the summer of the same year professional contract for the second division team of Caen. When he came off the bench on August 2, 2013 at the age of 17 years in the second division match against Dijon FCO in the 78th minute, he was able to record his professional debut. In the following time he came to other missions in the circle of the first team, where he was often summoned as a wildcard.
27 September 2011 Lemar debuted with a 0-0 draw against Ukraine for the French U- 17 team, for which he then regularly stood on the court. He took part in the France U-17 Championship 2012, but resigned from after the first round. He then moved on to the U-18 team for the season 2012/13. After the summer break of 2013, the recording was followed in the U- 19th