convert tif -format pdfa do not produce pdf/a but pdf...

[manufv]

hello,

I'm searching to product a pdf/a1-b (ISO ISO 19005-1 Level B) output from a tif file.
I use ImageMagick 7.0.7-4 Q16 x64 2017-09-23 on windows, command
magick convert file.tif -compress Group4 -format PDFA file.pdf
product a PDF Portable Document Format
I need a PDFA Portable Document Archive Format
magick mogrify -format pdfa -write file.pdf file.tif .... no best result....
in any case, it produce a PDF/PDF Portable Document Format.
....
here is my image https://1drv.ms/u/s!AiMQKzhNsuzMhrYyntxZYdouc7QEVg

thanks for any help

[manufv]

ok, I found a syntax which produce a PDFA :
magick convert file.tif pdfa:file.pdf but ... I'v got errors when i validate it at https://www.pdf-online.com/osa/validate.aspx
Validating file "file.pdf" for conformance level pdfa-3b
The file header format does not conform to the standard.
A device-specific color space (DeviceGray) without an appropriate output intent is used.
The document does not conform to the requested standard.
The file format (header, trailer, objects, xref, streams) is corrupted.
The document contains device-specific color spaces.
The document's meta data is either missing or inconsistent or corrupt.
The document does not conform to the PDF/A-3b standard.

Any idea which params I can add to magick/convert ?
thx