The 18-year-old Welsh attacking midfielder has been training with the Gladiators for some time.
He had been playing for Briton Ferry in the Cmyru South League before his move to the League One side.
At Vale, he was in their U18s squad and has netted three times in seven appearances this term.
Crewe-based Cadeau was also part of the history-making Welsh schools squad that captured the Centenary Shield in 2022.
Matlock boss Martin Carruthers is hoping to see Cadeau play a key role for the club moving forward.
“He was already training with Matlock but we couldn’t sign him earlier due to him having a ban while with Port Vale,” he said.
“But he’s keen, enthusiastic, fit, and can do a good job for us up and down the right.”
Cadeau goes straight into contention for Saturday’s trip to Stafford Rangers, where the Gladiators will go in search of a first victory in all competitions since Boxing Day.
Photo credit: Duncan Thomas
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