A senior official in the Washington office of the Small Business Administration demanded that local businesses make payments on her home mortgage, build a deck on her house at no charge and provide her with free use of a Cadillac, according to an indictment handed up yesterday.

Barbara J. Ivory, 42, of Oxon Hill, was charged in federal court in Alexandria with conspiracy, accepting gratuities and lying to a grand jury in connection with alleged activities from 1986 to early last year.

Ivory, who negotiated and administered federal contracts with minority-owned businesses in the Washington area, allegedly asked executives of local companies to provide her with money or other items in exchange for contract modifications that would bolster the companies' profits.

In the fall of 1987, an executive of the Baltimore-based Mel McLaughlin Company cashed a $5,000 corporate check and delivered the money to Ivory's home at her request, according to the indictment. Ivory signed Small Business Administration documents that helped the company, the indictment states.

The McLaughlin company also built a deck on Ivory's house, paying for materials and labor with money provided by another Washington area contractor, according to the indictment.

John F. Mercer, Ivory's attorney, said last night he had not seen the indictment and could not comment. If convicted, Ivory could face up to 21 years in prison and $250,000 in fines on each of the six counts.

Graph-Tech Inc., of Arlington, one of the companies named in the case, was indicted on separate charges yesterday for allegedly trying to trick the Defense Department into paying for personal expenses, including a holiday in Jamaica and a Gucci handbag.

The company and its three principal owners, Samuel A. Taylor, Angela D. Taylor and James T. Taylor, were accused of 51 felonies, including conspiracy, false claims and mail fraud.

Graph-Tech executives submitted illegal expense reports for work they said was done in the mid-1980s on a contract involving a Navy weapons program, according to the indictment. The Taylors also told employees to inflate their reports of hours worked, despite warnings from a Graph-Tech financial officer that such action would violate federal law, the indictment says.