Add cert file in retrofit request

I'm trying to integrate a banking API in my mobile app (Android) and, being in sandbox mode, I have a public key (the certificate) and private key that should be on each request. In doc, this is how the request looks like:

curl -i -k --cert public.cert --cert-type PEM --key private.key --key-type PEM "endpoint.com" -H "Correlation-ID: OK1200" -H "WEB-API-Key: MY_API_KEY" -H "Authorization: Bearer MY_TOKEN"

So, being in sandbox mode, how should I add both private key and public key to my retrofit requests?

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