Canon EOS 5D Mark IV is supported as part of the system since macOS 10.12.2 Sierra, as shown here, and the most recent applications installed by Sierra, like Photos for Mac can use it.
Digital camera RAW formats supported by iOS 10 and macOS Sierra - Apple Support
But as far as I can tell Aperture is not able to use the RAW support for the new cameras released with macOS 10.12.2, only the earlier released RAW support.
There have been posts, that Aperture does not recognize the RAW files for several of the cameras on this list:
Canon EOS 5D Mark IV
Canon EOS M5
Fujifilm X-T23
Nikon D3400
Panasonic LUMIX DMC-G8 / G80 / G85
Panasonic LUMIX DMC-LX9 / LX10 / LX15
Panasonic LUMIX DMC-FZ2500
Pentax K-70
See for example this discussion: Re: Re: Aperture and Fuji XT2 RAW files.
When I check the installed RawCamera.bundle, that Aperture is using, in the Terminal, the newest Canon is not listed in this bundle, only the MarkII and III.
strings /System/Library/CoreServices/RawCamera.bundle/Contents/MacOS/RawCamera | grep EOS5D
dng.adobe.CanonEOS5D
RCID_CanonEOS5D
RCID_CanonEOS5DMarkII
RCID_CanonEOS5DMarkIII
RCID_CanonEOS5DMarkIII_sraw
RCID_CanonEOS5DMarkII_sraw
RCID_CanonEOS5D dng
RCID_CanonEOS5DMarkII dng
dng.adobe.CanonEOS5DMarkII
RCID_CanonEOS5DMarkIII dng