Java SSH clinet using jcabi facing a FileNoFoundException

Question

I'm trying to use the jcabi library in order to ssh-connect a java application to a remote ubuntu server.

I'm using the following code sample

String host = "XX.XX.XX.XX";
String user = "myuser";
String key = "C:\path\to\the\pem\folder\relevantFile.pem"
String pwd = new Shell.Plain(
                new Ssh(host, 22,
                        user, key
                )
        ).exec("pwd");
System.out.println(hello);

When trying to run the code (it is in a @Test class BTW) I get the following error:

Caused by: java.io.FileNotFoundException: C:\....\AppData\Local\Temp\jcabi-ssh201869605540056323.key (The filename, directory name, or volume label syntax is incorrect)
at java.io.FileInputStream.open0(Native Method)

I also tried to set in the key, the content of the pem file, but the exception is the same.