How to Upload a Base64-encoded file to Media via Rest-API

Hi, I can upload media files as a “local file” but no base64-encoded files. What works with a file on my computer is:

curl --location --request POST 'https://[hostname]/wp-json/wp/v2/media/' \
--header 'Authorization: Basic [...]' \
--form 'title="000 Test via Curl"' \
--form 'caption="Text der Caption"' \
--form 'description="Text der Description"' \
--form 'alt_text="Text alternative"' \
--form 'file=@"/Users/.../Desktop/File.jpg"'

But I want to upload already available Base64-strings and struggle to do so. Any hints?

Kind regards, Martin