Is the father obligated to slaughter a sheep for the 'aqiqah of his five-year-old daughter, given that he did not do so previously due to prevailing traditions that prevented him, even though he is financially capable and adheres to the Maliki school of thought?

You are not obligated to perform the 'Aqiqah for your daughter who has reached this age because, in the Maliki madhhab, the time for 'Aqiqah expires with the sunset of the seventh day after birth. There is another opinion within the madhhab that it does not expire with the end of the first week, but rather it should be done in the second week. If it is not done then, it should be done in the third week. If it is not done then, it is forfeited. The 'Aqiqah in the Maliki madhhab is considered recommended (mandub).