{% raw %}
apiVersion: external-secrets.io/v1
kind: ExternalSecret
metadata:
  name: template
spec:
  # ...
  target:
    template:
      type: kubernetes.io/tls
      engineVersion: v2
      data:
        tls.crt: "{{ .mysecret | pkcs12cert }}"
        tls.key: "{{ .mysecret | pkcs12key }}"

        # if needed unlock the pkcs12 with the password
        tls.crt: "{{ .mysecret | pkcs12certPass "my-password" }}"

{% endraw %}