The former Nantes striker, signed for Cardiff City and was due to report to training but unfortunately died in a plane crash in the English channel on 21st January, 2019.
Cardiff City have refused to pay the transfer fee after Sala’s death as they think some details in his contract were still to be concluded and the transfer had not been finalized.
On Monday, FIFA ordered Cardiff City to pay €6million (£5.3million) as first installment to Nantes but the Bluebirds have decided to exercise the option in the ruling that requires them to file an appeal if they think otherwise.
The Championship club statement said, "Cardiff City FC is extremely disappointed at the decision of the Players Status Committee to award against the club. It would appear the committee has reached its conclusion on a narrow aspect of the overall dispute, without considering the full documentation presented by Cardiff City FC to FIFA.
"Nevertheless there remains clear evidence that the transfer agreement was never completed in accordance with multiple contractual requirements which were requested by Nantes, thereby rendering it null and void.
"We shall be appealing to CAS in order to seek a decision which considers all of the relevant contractual information and provides clarity on the full legal situation between our two clubs.
"This is a complex matter, which includes ongoing civil and criminal considerations both in the UK and abroad, which will likely have an impact on the validity of the transfer. It is therefore vital that a comprehensive judgement is reached following a full assessment and review of the facts."
It has been reported that Cardiff will also be liable for the other instalments agreed between the clubs, but FIFA stated it could not comment on this for "confidentiality reasons".
Cardiff City were relegated from the Premier league last season after a poor run of form.
