(a) Persons other than contractors or subcontractors. No lien shall be allowed in favor of any person other than a contractor or subcontractor, as defined herein, even though such person furnishes labor or materials to an improvement.

(b) Public purpose. No lien shall be allowed for labor or materials furnished for a purely public purpose.

(c) Conveyance prior to lien. If the property by conveyed in good faith and for a valuable consideration prior to the filing of a claim for alterations or repairs, the lien shall be wholly lost.

(d) Leasehold premises. No lien shall be allowed against the estate of an owner in fee by reason of any consent given by such owner to a tenant to improve the leased premises unless it shall appear in writing signed by such owner that the erection, construction, alteration or repair was in fact for the immediate use and benefit of the owner.

(e) Security interests. No lien shall be allowed for that portion of a debt representing the contract price of any materials against which the claimant holds or has claimed a security interest under the Pennsylvania Uniform Commercial Code or to which he has reserved title or the right to reacquire title.