garageband pc compatibility

I am using Garageband on my mac. I created a file and sent it to my bandmate who is using a Windows version of Garageband. Her Garageband won't open my file. Is there a way to save my Garageband file so that it can be opened by a PC?

These days one can easily share files from application such as Excel and Powerpoint so I am surprised this is even occuring.

Thanks in advance.