Thanks Matt,
It is now working with the following code:
string searchTerm = languageTerm.ToUpper();
IPredicateExpression filter = new PredicateExpression();
FieldLikePredicate caseInSenstivefilter = new FieldLikePredicate(LanguagetermFields.Languageterm, searchTerm);
caseInSenstivefilter.CaseSensitiveCollation = true;
filter.Add(caseInSenstivefilter);