Markelic, who is the Lions' top goal scorer, will remain with the United Counties League side until the end of the 2023/24 season due to the club's involvement in the Derbyshire Senior Cup final at Pride Park.
The youngster has previously played for the likes of Loughborough Dynamo and Corby Town.
On signing Markelic for the 2024/25 season, Ilkeston Town manager Ian Deakin said: "Sacha is an exciting young forward who we have been watching for a while.
"He has scored plenty of goals and possesses raw pace along with a real goalscoring threat.
"He has lots of potential and we are delighted to secure his signature with lots of clubs in competition for it higher up the pyramid with him in high demand.
"He will remain at Heanor for the remainder of this season in an agreement between both clubs to continue his development."
Photo credit: Ilkeston Town
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