Biased ex-colleague torpedoes my candidacy at a big corporation which currently employs him. Anything I can do?

The full story: Several years ago I worked at a medium-sized tech company. At a workplace get-together I met another engineer, we'll call him Benedict, who worked at a different organizational uni

The full story: Several years ago I worked at a medium-sized tech company. At a workplace get-together I met another engineer, we'll call him Benedict, who worked at a different organizational unit. We started chatting about our experience in the company and he seemed instantly impressed by the fact I was promoted twice within two years. Later he confessed that he didn't always have the necessary knowledge and skills to handle his current task queue, and we talked about how the company lacked a proper mentorship program. I started asking him about the exact nature of his duties, and it turned out to be very similar to the work I've done prior to my promotions. So, I offered to mentor him informally: I gave him my email so he could contact me whenever he had questions or wanted my input on any sort of problem or challenge at work. Benedict acted extremely grateful. He made use of my invitation several times over the next couple of years, and always wrote back appreciative comments about how much my informal mentorship was helping him. After these two years I started interviewing with other companies. With so much explicit trust and gratitude from Benedict, I felt comfortable asking him to serve as one of my references. When Google asked me for references, I provided his name as one of 3 current co-workers who would recommend me. Then something weird happened. My Google recruiter, who had previously told me I've done very well on their onsite, suddenly called to inform me they are terminating my process. In retrospect, I should have been extremely suspicious, but I shrugged it off as just a random misfortune. By that time I had offers from a few other companies, not quite as great as Google but still pretty good. I formally resigned my current role to attend all the remaining onsite invitations quickly. Two weeks later I get a call from a former co-worker who moved on to a senior engineering role at one of those other companies where I've been interviewing. He wondered why I provided a reference that had nothing but extremely negative things to say about me. I was shocked. Turned out Benedict was describing me as a very poor performer who gets ahead by playing politics and manipulating better engineers. When I explained that Benedict doesn't even work in the same organizational unit and wouldn't know anything about my daily work performance, my contact said that's not what his feedback reflected; on the contrary, he pretended to be intimately familiar with my ongoing work. Confused more than anything, I called Benedict immediately, and asked him point blank if he was saying these things. The same guy who was ever so appreciative and grateful before, now took a few moments of silence, then hung up the call without saying a word. Probably the closest thing to an admission I will ever get from him, as I never heard from him again. Fast forward to the present. I just finished another onsite with Google recently. My recruiter said feedback was "terrific" and all my interviewers strongly recommended a "hire" decision. Both her and another recruiter handling my candidacy rated my chances of an offer as very high. Then I got to the Hiring Committee and was rejected. I asked my recruiter how that was possible given my highly positive onsite feedback, and she only said that during the committee's discussion there appeared "another source of feedback" that caused this rejection. My spidey sense started tingling and I looked up Benedict online, only to discover he has been working at Google, at the same office where I applied... Thus I strongly suspect it is Benedict who provided his usual negative and false review of "my performance" and killed my candidacy a second time. Is there anything I can do about this? Or should I just accept that as long as Benedict works at Google, I will be barred from one of the largest and best tech companies in the market? TL;DR A former co-worker I informally mentored and trusted has been providing extremely negative false reviews of my past performance. He currently works at Google and seems to be torpedoing my candidacy there. Anything I can do?